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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2014	Mar. 02, 2015	Jun. 30, 2014
Document and Entity Information
Entity Registrant Name	VERACYTE, INC.
Entity Central Index Key	0001384101
Document Type	10-K
Document Period End Date	Dec. 31, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 122.4
Entity Common Stock, Shares Outstanding		22,551,242
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 35,014	$ 71,220
Accounts receivable, net of allowance of $84 and $107 as of December 31, 2014 and 2013	3,050	1,143
Supplies inventory	3,696	2,567
Prepaid expenses and other current assets	1,218	1,477
Deferred tax asset	300
Restricted cash	70
Total current assets	43,348	76,407
Property and equipment, net	4,161	2,952
In-process research and development	16,000
Goodwill	1,057
Restricted cash	118	118
Other assets	155	153
Total assets	64,839	79,630
Current liabilities:
Accounts payable	7,397	5,294
Accrued liabilities	7,851	7,594
Deferred Genzyme co-promotion fee	1,897	2,500
Total current liabilities	17,145	15,388
Long-term debt	4,923	4,899
Deferred tax liability	300
Deferred rent, net of current portion	149	286
Deferred Genzyme co-promotion fee, net of current portion	948	2,614
Total liabilities	23,465	23,187
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized, 0 shares issued and outstanding as of December 31, 2014 and 2013
Common stock, $0.001 par value; 125,000,000 shares authorized, 22,523,529 and 21,143,313 shares issued and outstanding as of December 31, 2014 and 2013	23	21
Additional paid-in capital	156,373	142,071
Accumulated deficit	(115,022)	(85,649)
Total stockholders' equity	41,374	56,443
Total liabilities and stockholders' equity	$ 64,839	$ 79,630

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance (in dollars)	$ 84	$ 107
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	22,523,529	21,143,313
Common stock, shares outstanding	22,523,529	21,143,313

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue	$ 38,190	$ 21,884	$ 11,628
Operating expenses:
Cost of revenue	16,606	12,607	7,584
Research and development	9,804	7,810	6,608
Selling and marketing	21,932	12,540	8,447
General and administrative	18,854	12,100	7,918
Total operating expenses	67,196	45,057	30,557
Loss from operations	(29,006)	(23,173)	(18,929)
Interest expense	(439)	(233)
Other income (expense), net	72	(2,174)	280
Net loss	(29,373)	(25,580)	(18,649)
Comprehensive loss	$ (29,373)	$ (25,580)	$ (18,649)
Net loss per common share, basic and diluted (in dollars per share)	$ (1.36)	$ (6.15)	$ (28.68)
Shares used to compute net loss per common share, basic and diluted (in shares)	21,639,374	4,158,664	650,333

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Convertible Preferred Stock.	Series C	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2011	$ 49,296
Balance (in shares) at Dec. 31, 2011	45,147,999
Balance at Dec. 31, 2011			$ 1	$ 653	$ (41,420)	$ (40,766)
Balance (in shares) at Dec. 31, 2011			594,941
Increase (Decrease) in Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of convertible preferred stock, net of issuance costs and preferred stock liability		$ 14,076
Issuance of convertible preferred stock, net of issuance costs and preferred stock liability (in shares)		7,936,508
Issuance of common stock on exercise of stock options				76		$ 76
Issuance of common stock on exercise of stock options (in shares)			72,743			72,743
Stock-based compensation expense (employee)				590		$ 590
Stock-based compensation expense (non-employee)				85		85
Equity-based compensation				193		193
Net loss					(18,649)	(18,649)
Comprehensive loss					(18,649)	(18,649)
Balance at Dec. 31, 2012	$ 63,372
Balance (in shares) at Dec. 31, 2012	53,084,507
Balance at Dec. 31, 2012			$ 1	1,597	(60,069)	(58,471)
Balance (in shares) at Dec. 31, 2012			667,684
Increase (Decrease) in Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of convertible preferred stock, net of issuance costs and preferred stock liability		$ 12,997
Issuance of convertible preferred stock, net of issuance costs and preferred stock liability (in shares)		6,904,761
Extinguishment of the preferred stock liability	$ 2,653
Issuance of common stock on exercise of stock options				552		$ 552
Issuance of common stock on exercise of stock options (in shares)			377,966			377,966
Issuance of common stock in initial public offering, net of discounts and commissions of $4,642 and issuance costs of $2,507			$ 5	59,151		$ 59,156
Issuance of common stock in initial public offering, net of discounts and commissions of $4,642 and issuance costs of $2,507 (in shares)			5,100,351
Conversion of preferred stock into common stock upon initial public offering	$ (79,022)		$ 15	79,007		79,022
Conversion of preferred stock into common stock upon initial public offering (in shares)	(59,989,268)		14,997,312
Reclassification of preferred stock warrant liability into additional paid-in capital upon initial public offering				261		261
Common stock subject to repurchase				(3)		(3)
Stock-based compensation expense (employee)				1,041		1,041
Stock-based compensation expense (non-employee)				206		206
Equity-based compensation				259		259
Net loss					(25,580)	(25,580)
Comprehensive loss					(25,580)	(25,580)
Balance at Dec. 31, 2013			$ 21	142,071	(85,649)	56,443
Balance (in shares) at Dec. 31, 2013			21,143,313
Increase (Decrease) in Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of common stock on exercise of stock options			$ 1	674		$ 675
Issuance of common stock on exercise of stock options (in shares)			402,100			402,100
Issuance of common stock on cashless exercise of warrant (in shares)			13,739
Common stock subject to repurchase				3		$ 3
Issuance of common stock for acquisition			$ 1	10,077		10,078
Issuance of common stock in the merger acquisition (in shares)			964,377
Stock-based compensation expense (employee)				3,388		3,388
Stock-based compensation expense (non-employee)				160		160
Net loss					(29,373)	(29,373)
Comprehensive loss					(29,373)	(29,373)
Balance at Dec. 31, 2014			$ 23	$ 156,373	$ (115,022)	$ 41,374
Balance (in shares) at Dec. 31, 2014			22,523,529

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($)		1 Months Ended	2 Months Ended	12 Months Ended
	Nov. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Issuance of convertible preferred stock, preferred stock liability					$ 861,000
Issuance of common stock in initial public offering, discounts and commissions				$ 4,642,000
Issuance of common stock in initial public offering, issuance cost				$ 2,507,000
Series C
Issuance of convertible preferred stock, issue price (in dollars per share)		$ 1.89	$ 1.89		$ 1.89
Issuance of convertible preferred stock, issuance cost	$ 53.00	$ 53.00	$ 63,000
Issuance of convertible preferred stock, preferred stock liability			$ 861,000

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net loss	$ (29,373)	$ (25,580)	$ (18,649)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,175	999	706
Bad debt expense	54	109	225
Genzyme co-promotion fee amortization	(2,269)	(2,500)	(2,386)
Stock-based compensation	3,548	1,247	675
Equity-based compensation			259
Amortization of debt discount and issuance costs	97	56
Interest on debt balloon payment	81	42
Change in value of preferred stock liability		2,070	(278)
Change in value of preferred stock warrant liability		86
Changes in operating assets and liabilities:
Accounts receivable	(1,961)	(683)	(565)
Supplies inventory	(1,129)	(1,517)	(771)
Prepaid expenses and current other assets	(38)	(722)	(191)
Other assets	(46)	24	(119)
Accounts payable	1,874	3,348	1,348
Accrued liabilities and deferred rent	355	3,862	2,579
Deferred Genzyme co-promotion fee			10,000
Net cash used in operating activities	(27,632)	(19,159)	(7,167)
Investing activities
Purchases of property and equipment	(2,024)	(1,332)	(1,462)
Cash remitted for acquisition, net of cash received	(6,916)
Change in restricted cash	(70)	50
Net cash used in investing activities	(9,010)	(1,282)	(1,462)
Financing activities
Proceeds from the issuance of long-term debt, net of debt issuance costs		4,877
Payment of end-of-term obligation	(110)
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		12,945	14,989
Proceeds from issuance of common stock in initial public offering, gross		66,304
Commissions and issuance costs relating to the initial public offering	(129)	(7,019)
Proceeds from the exercise of common stock options	675	552	76
Net cash provided by financing activities	436	77,659	15,065
Net increase (decrease) in cash and cash equivalents	(36,206)	57,218	6,436
Cash and cash equivalents at beginning of period	71,220	14,002	7,566
Cash and cash equivalents at end of period	35,014	71,220	14,002
Supplementary cash flow information of non cash investing and financing activities:
Fair value of common stock issued for acquisition	10,078
Non-cash issuance of long-term debt	5,000
Non-cash repayment of long-term debt	(5,000)
Purchases of property and equipment included in accounts payable and accrued liabilities	383	25	109
Non-cash purchases of property and equipment		257
Preferred stock liability			861
Transfer of preferred stock liability to equity		2,653
Convertible preferred stock issuance costs included in accounts payable			52
Preferred stock warrants		175
Conversion of preferred stock warrant liability to common stock warrants		261
Issuance of common stock from the non-cash exercise of common stock warrants	187
Conversion of convertible preferred stock to common stock		79,022
IPO costs included in accounts payable and accrued liabilities		129
Cash paid for interest on debt	$ 307	132
Transfer of equity-based compensation from liabilities to equity		$ 259	$ 193

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2014
Organization and Description of Business
Organization and Description of Business	1. Organization and Description of Business Veracyte, Inc. (the "Company") was incorporated in the state of Delaware on August 15, 2006 as Calderome, Inc. Calderome operated as an incubator until early 2008. On March 4, 2008, the Company changed its name to Veracyte, Inc. Veracyte is a diagnostics company pioneering the field of molecular cytology to improve patient outcomes and lower healthcare costs. The Company specifically targets diseases that often require invasive procedures for an accurate diagnosis—diseases where many healthy patients undergo costly interventions that ultimately prove unnecessary. The Company improves the accuracy of diagnosis at an earlier stage of patient care by deriving clinically actionable genomic information from cytology samples. The Company's first commercial solution, the Afirma® Thyroid FNA Analysis, includes as its centerpiece the Gene Expression Classifier ("GEC"). The GEC helps physicians reduce the number of unnecessary surgeries by employing a proprietary 142-gene signature to preoperatively determine whether thyroid nodules previously classified by cytopathology as indeterminate can be reclassified as benign. The comprehensive offering also includes cytopathology testing and the Afirma Malignancy Classifiers, launched in May 2014. The Company markets and sells Afrma through a co-promotion agreement with Genzyme Corporation, a subsidiary of Sanofi. On September 16, 2014, the Company acquired Allegro Diagnostics Corp. ("Allegro") to accelerate its entry into pulmonology, the Company's second planned clinical area. Allegro was a privately-held company based in Maynard, Massachusetts, focused on the development of genomic tests to improve the preoperative diagnosis of lung cancer. See Note 4. The Company intends to enter the lung cancer diagnostics market by mid-2015 with the Percepta™ Bronchial Genomic Classifier ("Percepta"), a test designed to resolve diagnostic ambiguity among the approximately 250,000 patients in the United States who undergo bronchoscopy each year to assess potentially cancerous lung nodules. The Company's operations are based in South San Francisco, California and Austin, Texas, and it operates in one segment in the United States. Initial Public Offering On November 4, 2013, the Company completed an initial public offering ("IPO") of its common stock. In connection with its IPO, the Company issued and sold 5,100,351 shares of common stock at a price to the public of $13.00 per share. As a result of the IPO, the Company received $59.2 million in net proceeds, after deducting underwriting discounts and commissions of $4.6 million and offering expenses of $2.5 million payable by the Company. In connection with the IPO, the Company's outstanding shares of convertible preferred stock were automatically converted into 14,997,312 shares of common stock.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2014

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The Company's consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP"). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Significant items subject to such estimates include: revenue recognition; contractual allowances; allowance for doubtful accounts; the useful lives of property and equipment; the recoverability of long-lived assets; the estimation of the fair value of intangible assets; the determination of fair value of the Company's common stock prior to the Company's IPO; stock options; preferred stock liability; income tax uncertainties, including a valuation allowance for deferred tax assets; and contingencies. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenue and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions.

Liquidity

The Company has incurred net losses since its inception and expects to incur additional losses in 2015 and in future years. As of December 31, 2014, the Company had an accumulated deficit of $115.0 million. The Company may never achieve revenue sufficient to offset its expenses. The Company believes its cash and cash equivalents of $35.0 million as of December 31, 2014 and its revenue from the sale of Afirma in 2015 will be sufficient to meet its anticipated cash requirements for at least the next 12 months.

If the Company is not able to generate revenue to finance its cash requirements, the Company will need to finance future cash needs primarily through public or private equity offerings, debt financings, borrowings or strategic collaborations or licensing arrangements. If the Company is not able to secure additional funding when needed, on acceptable terms, it may have to delay, reduce the scope of or eliminate one or more research and development programs or selling and marketing initiatives which may have a material adverse effect on the Company's business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all.

Concentrations of Credit Risk and Other Risks and Uncertainties

The Company's cash and cash equivalents are deposited with one major financial institution in the United States, as required by the loan and security agreement discussed in Note 8. Deposits in this institution may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses on its deposits of cash and cash equivalents.

Several of the components of the Company's sample collection kit and test reagents are obtained from single-source suppliers. If these single-source suppliers fail to satisfy the Company's requirements on a timely basis, it could suffer delays in being able to deliver its diagnostic solution, a possible loss of revenue, or incur higher costs, any of which could adversely affect its operating results.

The Company is also subject to credit risk from its accounts receivable related to its sales of Afirma. The Company generally does not perform evaluations of customers' financial condition and generally does not require collateral.

Through December 31, 2014, all of the Company's revenue have been derived from the sale of Afirma. The Company's solution to date has been delivered primarily to physicians in the United States. The Company's third-party payers in excess of 10% of revenue and their related revenue as a percentage of total revenue were as follows:

	Year Ended December 31,
	2014			2013			2012
Medicare		26	%		32	%		34	%
Aetna		11	%		9	%		13	%
United Healthcare		18	%		18	%		12	%

		55	%		59	%		59	%

As the number of payers reimbursing for Afirma increases, the percentage of revenue derived from Medicare and other significant third-party payers has changed and will continue to change as a percentage of total revenue.

The Company's significant third-party payers and their related accounts receivable balance at December 31, 2014 and 2013 as a percentage of total accounts receivable are as follows:

	December 31,
	2014			2013
Medicare		64	%		78	%
Aetna		12	%		—
United Healthcare		14	%		3	%

No other third-party payer represented more than 10% of the Company's accounts receivable balances for these periods.

Cash Equivalents

Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. Cash equivalents consist primarily of amounts invested in a money market account primarily consisting of U.S. Treasury reserves.

Restricted Cash

The Company reserved $70,000 in cash as of December 31, 2014 to cover liabilities associated with the acquisition of Allegro as discussed in Note 4. This restricted cash is included in current assets on the Company's consolidated balance sheet.

The Company had long-term deposits of $118,000 as of December 31, 2014 and 2013, restricted from withdrawal and held by a bank in the form of collateral for letters of credit. The balance for each period consists of a letter of credit totaling $118,000 held as security for the lease of the Company's office space in South San Francisco, California. This restricted cash is included in long-term assets on the Company's consolidated balance sheets.

Allowance for Doubtful Accounts

The Company estimates an allowance for doubtful accounts against its individual accounts receivable based on estimates of expected reimbursement consistent with historical payment experience in relation to the amounts billed. Bad debt expense is included in general and administrative expense on the Company's statements of operations and comprehensive loss. Accounts receivable are written off against the allowance when there is substantive evidence that the account will not be paid.

The balance of allowance for doubtful accounts as of December 31, 2014 and 2013, including charges to bad debt expense and write-offs, net of recoveries, was as follows:

	As of December 31,
	2014			2013
	(In thousands)
Beginning balance	$	107		$	222
Charged to expense		54			109
Write-offs, net of recoveries		(77	)		(224	)

Ending balance	$	84		$	107

Supplies Inventory

Supplies inventory consists of test reagents and other consumables used in the sample collection kits and in cytopathology and GEC test processing and are valued at the lower of cost or market value. Cost is determined using actual costs on a first-in, first-out basis.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements and betterments are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized.

Internal-use Software

The Company capitalizes costs incurred in the application development stage to design and implement the software used in the tracking and reporting of laboratory activity. Costs incurred in the development of application software are capitalized and amortized over an estimated useful life of three years on a straight line basis. The total cost, accumulated depreciation and net book value was $927,000, $330,000 and $597,000, respectively, as of December 31, 2014, and was $482,000, $195,000 and $287,000, respectively, as of December 31, 2013, and are included in property and equipment in the Company's consolidated balance sheets. During the years ended December 31, 2014 and 2013, the Company capitalized $445,000 and $212,000, respectively, of software development costs. Amortization expense totaled $135,000, $108,000 and $47,000 in the years ended December 31, 2014, 2013 and 2012, respectively.

Business Combination

The Company accounts for acquisitions using the acquisition method of accounting which requires the recognition of tangible and identifiable intangible assets acquired and liabilities assumed at their estimated fair values as of the business combination date. The Company allocates any excess purchase price over the estimated fair value assigned to the net tangible and identifiable intangible assets acquired and liabilities assumed to goodwill. Transaction costs are expensed as incurred in general and administrative expenses. Results of operations and cash flows of acquired companies are included in the Company's operating results from the date of acquisition.

Goodwill

Goodwill, derived from the Company's acquisition of Allegro, is reviewed for impairment on an annual basis or more frequently if events or circumstances indicate that it may be impaired. The Company's goodwill evaluation is based on both qualitative and quantitative assessments regarding the fair value of goodwill relative to its carrying value. The Company has determined that it operates in a single segment and has a single reporting unit associated with the development and commercialization of diagnostic products. In the event the Company determines that it is more likely than not the carrying value of the reporting unit is higher than its fair value, quantitative testing is performed comparing recorded values to estimated fair values. If impairment is present, the impairment loss is measured as the excess of the recorded goodwill over its implied fair value. The Company performs its annual evaluation of goodwill during the fourth quarter of each fiscal year. There was no impairment for the year ended December 31, 2014.

Intangible Assets

The Company's intangible assets are comprised of acquired in-process research and development, or IPR&D. The fair value of IPR&D acquired through a business combination is capitalized as an indefinite-lived intangible asset until the completion or abandonment of the related research and development activities. IPR&D is tested for impairment annually or when events or circumstances indicate that the fair value may be below the carrying value of the asset. There was no impairment for the year ended December 31, 2014. If and when research and development is complete, the associated assets would then be amortized over their estimated useful lives.

Impairment of Long-lived Assets

The Company annually reviews long-lived and indefinite lived assets other than goodwill for impairment or whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. The Company recognizes an impairment loss when the total of estimated future undiscounted cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, would be assessed using discounted cash flows or other appropriate measures of fair value. There were no impairments for the years ended December 31, 2014 and 2013.

Bonus Accruals

The Company accrues for liabilities under discretionary employee and executive bonus plans. These estimated compensation liabilities are based on progress against corporate objectives approved by the Board of Directors, compensation levels of eligible individuals, and target bonus percentage levels. The Board of Directors and the Compensation Committee of the Board of Directors review and evaluate the performance against these objectives and ultimately determine what discretionary payments are made. The Company accrued $1.1 million as of December 31, 2014 and 2013 for liabilities associated with these employee and executive bonus plans which are included in accrued liabilities in the Company's consolidated balance sheets.

Fair Value of Financial Instruments

The carrying amounts of certain financial instruments including cash and cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities.

Revenue Recognition

The Company's revenue is generated from the provision of diagnostic services using the Afirma solution. The Company's service is completed upon the delivery of test results to the prescribing physician which triggers the billing for the service. The Company recognizes revenue related to billings for Medicare and commercial payers on an accrual basis, net of contractual adjustments, when a reasonable estimate of reimbursement can be made. These contractual adjustments represent the difference between the list price (the billing rate) and the reimbursement rate for each payer. Upon ultimate collection, the amount received from Medicare and commercial payers where reimbursement was estimated is compared to previous estimates and the contractual allowance is adjusted accordingly. Until a contract has been negotiated with a commercial payer or governmental program, the Afirma solution may or may not be covered by these entities' existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance declines to reimburse the Company. In the absence of an agreement with the patient or other clearly enforceable legal right to demand payment from the patient, the related revenue is only recognized upon the earlier of payment notification, if applicable, or cash receipt.

For all services performed, the Company considers whether or not the following revenue recognition criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; and a reasonable estimate of reimbursement can be made.

Persuasive evidence of an arrangement exists and delivery is deemed to have occurred upon delivery of a patient report to the prescribing physician. The assessment of whether a reasonable estimate of reimbursement can be made requires significant judgment by management. Where management's judgment indicates a reasonable estimate of reimbursement can be made, revenue is recognized upon delivery of the patient report. Some patients have out-of-pocket costs for amounts not covered by their insurance carrier, and the Company may bill the patient directly for these amounts in the form of co-payments and co-insurance in accordance with their insurance carrier and health plans. Some payers may not cover the Company's GEC as ordered by the prescribing physician under their reimbursement policies. The Company pursues reimbursement from such patients on a case-by-case basis. In the absence of contracted reimbursement coverage or the ability to reasonably estimate reimbursement, the Company recognizes revenue upon receipt of third-party payer notification of payment or when cash is received.

Revenue recognized when cash is received was $25.7 million, $14.6 million and $7.5 million for the years ended December 31, 2014, 2013 and 2012, respectively. Revenue recognized on an accrual basis was $12.5 million, $7.3 million and $4.1 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Cost of Revenue

Cost of revenue is expensed as incurred and includes material and service costs, cytopathology testing services performed by a third-party pathology group, stock-based compensation expense, direct labor costs, equipment and infrastructure expenses associated with testing samples, shipping charges to transport samples, and allocated overhead including rent, information technology, equipment depreciation and utilities.

Research and Development

Research and development costs are charged to operations as incurred. Research and development costs include, but are not limited to, payroll and personnel-related expenses, stock-based compensation expense, prototype materials, laboratory supplies, consulting costs, costs associated with setting up and conducting clinical studies at domestic and international sites, and allocated overhead including rent, information technology, equipment depreciation and utilities.

Income Taxes

The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized.

The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. The Company's assessment of an uncertain tax position begins with the initial determination of the position's sustainability and is measured at the largest amount of benefit that is more-likely-than-not of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit may change as new information becomes available.

Stock-based Compensation

Stock-based compensation expense for equity instruments issued to employees is measured based on the grant-date fair value of the awards. The fair value of each employee stock option is estimated on the date of grant using the Black-Scholes option-pricing model. The Company recognizes compensation costs on a straight-line basis for all employee stock based compensation awards that are expected to vest over the requisite service period of the awards, which is generally the awards' vesting period. Forfeitures are required to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

Equity awards issued to non-employees are valued using the Black-Scholes option-pricing model and are subject to re-measurement as the underlying equity awards vest.

Net Loss per Common Share

Basic net loss per common share is calculated by dividing net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. Diluted net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury stock method. Potentially dilutive securities consisting of options and warrants to purchase common stock are considered to be common stock equivalents and were excluded from the calculation of diluted net loss per common share because their effect would be anti-dilutive for all periods presented.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers, requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The updated standard will replace most existing revenue recognition guidance in GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. Early adoption is not permitted. The updated standard becomes effective for the Company in the first quarter of fiscal 2017. The Company has not yet selected a transition method and is currently evaluating the potential effect of the updated standard on its financial statements.

In August 2014, FASB issued Accounting Standards Update No. 2014-15, Presentation of Financial Statements Going Concern—Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern. The amendments require management to assess an entity's ability to continue as a going concern by incorporating and expanding upon certain principles that are currently in U.S. auditing standards. Specifically, the amendments: (1) provide a definition of the term substantial doubt; (2) require an evaluation every reporting period including interim periods; (3) provide principles for considering the mitigating effect of management's plans; (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management's plans; (5) require an express statement and other disclosures when substantial doubt is not alleviated; and (6) require an assessment for a period of one year after the date that the financial statements are issued (or available to be issued). ASU 2014-15 will be effective for annual periods ending after December 15, 2016 and interim periods within annual periods beginning after December 15, 2016 with early adoption permitted. ASU 2014-15 will be effective for the Company beginning with its annual report for fiscal 2016 and interim periods thereafter. The Company has not yet determined the effect of the adoption of this standard on the Company's consolidated financial statements.

Net Loss Per Common Share

12 Months Ended

Dec. 31, 2014

Net Loss Per Common Share

Net Loss Per Common Share

3. Net Loss Per Common Share

The following table presents the calculation of basic and diluted net loss per common share for the years ended December 31, 2014, 2013 and 2012 (in thousands, except share and per share amounts):

	Year Ended December 31,
	2014			2013			2012
Net loss	$	(29,373	)	$	(25,580	)	$	(18,649	)


Shares used to compute net loss per common share, basic and diluted		21,639,374			4,158,664			650,333


Net loss per common share, basic and diluted	$	(1.36	)	$	(6.15	)	$	(28.68	)

The following outstanding common stock equivalents have been excluded from diluted net loss per common share for the years ended December 31, 2014 and 2013 because their inclusion would be anti-dilutive:

	Year Ended December 31,
	2014		2013
Shares of common stock subject to outstanding options		3,249,469		2,359,287
Shares of common stock issuable upon exercise of warrants		—		24,801

Total shares of common stock equivalents		3,249,469		2,384,088

Business Combination

12 Months Ended

Dec. 31, 2014

Business Combination

Business Combination

4. Business Combination

On September 16, 2014, the Company acquired Allegro via a merger with Full Moon Acquisition, Inc., a wholly-owned subsidiary of the Company. Allegro was a privately-held company based in Maynard, Massachusetts, focused on the development of genomic tests to improve the preoperative diagnosis of lung cancer. Allegro merged with Full Moon, (the "Merger"), with Allegro surviving the Merger as a wholly-owned subsidiary of the Company. At the effective time of the Merger, each share of the common stock of Full Moon issued and outstanding immediately prior to the effective time of the Merger was automatically converted into one share of common stock of Allegro and represented the only outstanding common stock of Allegro at the effective time of the Merger; all previously issued and outstanding shares of common stock of Allegro were canceled. The Series A preferred stock of Allegro issued and outstanding immediately prior to the effective time of the Merger was canceled and automatically converted into the right to receive a total of 964,377 shares of the Company's common stock and $2.7 million in cash. Outstanding indebtedness of Allegro totaling $4.3 million was settled in cash by the Company on the effective date of the Merger. All outstanding stock options under Allegro's equity incentive plan were canceled.

The acquisition of Allegro is expected to accelerate the Company's molecular diagnostics business into the pulmonology diagnostics market. Allegro's lung cancer test is designed to help physicians determine which patients with lung nodules who have had a non-diagnostic bronchoscopy result are at low risk for cancer and can thus be safely monitored with CT scans rather than undergoing invasive procedures. The Company plans to launch its lung cancer test in the middle of 2015.

The Merger was accounted for using the acquisition method of accounting with the Company treated as the accounting acquirer. The purchase price was allocated based on the estimated fair value of the assets acquired and liabilities assumed at the date of the acquisition.

The Company incurred approximately $0.5 million in acquisition-related costs related to the Merger, which primarily consisted of legal, accounting and valuation-related expenses. In addition, the Company incurred $1.2 million related to transaction bonuses and severance payments to former Allegro employees associated with the Merger. These expenses were recorded in general and administrative expense in the accompanying consolidated statements of operations and comprehensive loss. Total expenses and net loss associated with the acquired Allegro business in the Company's consolidated statements of operations and comprehensive loss were not separately identifiable due to the integration with the Company's operations.

The acquisition consideration was comprised of (in thousands):

Stock	$	10,078
Cash		2,725
Payment of outstanding indebtedness		4,290

Total acquisition consideration	$	17,093

The stock consideration of $10.1 million was determined based on the closing price of the Company's common stock on September 16, 2014 ($10.45 per share).

The fair value of the assets acquired and liabilities assumed at the closing date of the Merger are summarized below (in thousands):

Cash and cash equivalents	$	29
Prepaid expenses		3
Other current assets		13
In-process research and development ("IPR&D")		16,000
Goodwill		1,057
Accrued liabilities		(9	)

Total net assets acquired	$	17,093

The fair value of IPR&D was determined using the multi-period excess earnings method of the income approach, which estimates the economic benefits of the IPR&D over multiple time periods by identifying the cash flows associated with the use of the asset, based on forecasts prepared by management, and deducting a periodic charge reflecting a fair return for the use of contributory assets. The forecasted cash flows were discounted based on a discount rate of 18.5%. The discount rate represents the Company's weighted average return on assets and was benchmarked against the internal rate of return and cost of capital of guideline publicly traded companies. The fair value of the IPR&D was capitalized as of the closing date of the Merger and is subsequently accounted for as an indefinite-lived intangible asset, tested for impairment at least annually, until completion or abandonment of the associated research and development activities. Once complete, amortization of the acquired IPR&D asset into earnings will commence. The Company estimates that the acquired IPR&D asset will have a useful life of less than 20 years after taking into consideration expected use of the asset, legal or regulatory provisions that may limit or extend the life of the asset, as well as the effects of obsolescence and other economic factors.

Goodwill, which represents the purchase price in excess of the fair value of net assets acquired, is not expected to be deductible for income tax purposes. This goodwill is reflective of the value derived from the expected acceleration of the Company's entry into the pulmonology market.

Pro Forma Financial Information (Unaudited)

The following pro forma financial information is based on the historical financial statements of the Company and presents the Company's results as if the Merger had occurred as of January 1, 2013 (in thousands):

	Year Ended December 31,
	2014			2013
Revenue	$	38,190		$	21,884


Net loss	$	(29,090	)	$	(28,605	)

The pro forma results present the combined historical results of operations with adjustments to reflect one-time charges including:

•	The reversal of costs related to transaction bonuses and other payments to employees and acquisition-related expenses directly related to the Merger of $2.2 million for the year ended December 31, 2014; and
•	the elimination of interest expense related to Allegro indebtedness of $2.3 million and $4.5 million for the years ended December 31, 2014 and 2013, respectively.

The pro forma information presented does not purport to present what the actual results would have been had the Merger actually occurred on January 1, 2013, nor is the information intended to project results for any future period.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472

Reference 8: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1524-128463

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Balance Sheet Components

12 Months Ended

Dec. 31, 2014

Balance Sheet Components

Balance Sheet Components

5. Balance Sheet Components

Property and Equipment, Net

Property and equipment consisted of the following (in thousands):

	Year Ended December 31,
	2014			2013
Leasehold improvements	$	788		$	779
Laboratory equipment		4,199			2,946
Computer equipment		875			645
Software, including software developed for internal use		1,353			901
Furniture and fixtures		197			189
Construction-in-process		739			307

Total property and equipment, at cost		8,151			5,767
Accumulated depreciation and amortization		(3,990	)		(2,815	)

Total property and equipment, net	$	4,161		$	2,952

Depreciation and amortization expense was $1,175,000, $999,000 and $706,000 for the years ended December 31, 2014, 2013 and 2012, respectively, and was recorded in the statements of operations and comprehensive loss as follows (in thousands):

	Year Ended December 31,
	2014		2013		2012
Cost of revenue	$	677	$	593	$	401
Research and development		187		179		184
Selling and marketing		101		54		46
General and administrative		210		173		75

Total depreciation and amortization expense	$	1,175	$	999	$	706

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	Year Ended December 31,
	2014		2013
Accrued compensation expenses	$	2,673	$	1,962
Accrued Genzyme co-promotion fees		3,309		4,915
Accrued other		1,869		717

Total accrued liabilities	$	7,851	$	7,594

Fair Value Measurements

12 Months Ended

Dec. 31, 2014

Fair Value Measurements

Fair Value Measurements

6. Fair Value Measurements

The Company records its financial assets and liabilities at fair value. The carrying amounts of certain financial instruments of the Company, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities. The carrying value of debt approximates its fair value because the interest rate approximates market rates that the Company could obtain for debt with similar terms. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value, and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows:

•	Level I: Inputs which include quoted prices in active markets for identical assets and liabilities.
•	Level II: Inputs other than Level I that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
•	Level III: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The fair value of the Company's financial assets, which consist only of money market funds, was $33.2 million and $70.0 million as of December 31, 2014 and December 31, 2013, respectively, and are Level I assets as described above.

The Company has no Level III liabilities as of December 31, 2014 and 2013. The following table sets forth the changes in the fair value of the Company's Level III financial liabilities, which consisted of a preferred stock liability during 2013, which were measured on a recurring basis (in thousands):

	December 31,
	2014		2013
Beginning balance	$	—	$	583
Change in fair value of preferred stock liability recorded as other expense, net		—		2,070
Settlement of preferred stock liability		—		(2,653	)
Fair value of preferred stock warrant liability		—		175
Change in fair value of preferred stock warrant liability recorded as other expense, net		—		86
Conversion of preferred stock warrant liability		—		(261	)

Ending balance	$	—	$	—

In November 2012, the Company recorded a preferred stock liability as investors received the right to purchase from the Company, on the same terms, additional shares of Series C convertible preferred stock, in a second tranche. As the investors held a majority of the board seats, the decision to complete the second tranche was deemed to be outside the control of the Company. The preferred stock liability was valued using the option-pricing method, which resulted in an initial fair value of $0.9 million for the Company's obligation to sell the convertible preferred stock. In June 2013, the Company settled the preferred stock liability upon completion of the sale of the second tranche of Series C convertible preferred stock. Immediately prior to settlement, the Company revalued the preferred stock liability to $2.7 million and recorded other expense of $2.1 million related to the change in value of the liability through that date. The preferred stock liability was valued using the option-pricing method with the following assumptions: 100% probability of success of the second tranche, fair value of Series C preferred stock of $2.39, a term of 0.003 years and expected volatility of 36.4%.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies

Commitments and Contingencies

7. Commitments and Contingencies

Operating Leases

The Company leases its headquarters and South San Francisco laboratory facilities under a non-cancelable lease agreement that expires March 31, 2016. The Company provided security deposits in the form of irrevocable standby letters of credit secured with restricted cash deposits at the Company's primary bank. The Company deposited $118,000 in restricted cash accounts as collateral for the lease which is included in restricted cash in the Company's consolidated balance sheets as of December 31, 2014 and 2013.

The Company also leases laboratory space in Austin, Texas. The lease expires on July 31, 2018. The Company provided a cash security deposit of $75,000, which is included in other assets in the Company's consolidated balance sheets as of December 31, 2014 and 2013.

Future minimum lease payments under non-cancelable operating leases as of December 31, 2014 are as follows (in thousands):

Year Ending December 31,	Amounts
2015	$	989
2016		413
2017		222
2018		130
Thereafter		—

Total minimum lease payments	$	1,754

The Company recognizes rent expense on a straight-line basis over the non-cancelable lease period. Facilities rent expense was $852,000, $840,000 and $711,000 for the years ended December 31, 2014, 2013 and 2012, respectively.

Supplies Purchase Commitments

The Company had a non-cancelable purchase commitment with two suppliers to purchase a minimum quantity of supplies for approximately $715,000 at December 31, 2014, all of which is expected to be paid in early 2015.

Debt Obligations

See Note 8, Debt.

Contingencies

From time to time, the Company may be involved in legal proceedings arising in the ordinary course of business. The Company believes there is no litigation pending that could have, individually or in the aggregate, a material adverse effect on the financial position, results of operations or cash flows.

Debt

12 Months Ended

Dec. 31, 2014

Debt

Debt

8. Debt

In June 2013, the Company entered into a loan and security agreement ("Original Loan") with a financial institution to fund its working capital and other general corporate needs. The Original Loan provided for term loans of up to $10.0 million in aggregate. The Company drew down $5.0 million in funds under the agreement in June 2013, and did not draw the remaining $5.0 million on or before the expiration date of March 31, 2014. The Company was required to repay the outstanding principal in 30 equal installments beginning 18 months after the date of the borrowing and was due in full in June 2017. The Original Loan had an interest rate of 6.06% per annum, carried prepayment penalties of 2.25% and 1.50% for prepayment within one and two years, respectively, and 0.75% thereafter.

In December 2014, the Company amended certain terms and conditions of the Original Loan ("Amended Loan"). The Amended Loan provides for term loans of up to $15.0 million in aggregate, in three tranches of $5.0 million each. The Company borrowed $5.0 million under the first tranche in December 2014 and used the funds for repayment of the $5.0 million in principal outstanding under the Original Loan, in a cashless transaction. In addition, the Company paid the accrued but unpaid interest of $14,000 due on the Original Loan and the related end-of-term payment of $110,000. The Amended Loan waived the prepayment premium of $75,000 under the Original Loan and reduced the end-of-term payment of $225,000 under the Original Loan to $110,000. The second $5.0 million tranche under the Amended Loan is available through December 31, 2015 and the Company may borrow the third $5.0 million tranche any time through June 30, 2016 after achieving the third tranche revenue milestone as defined in the Amended Loan.

The carrying value of the debt approximates its fair value because the interest rate approximates market rates that the Company could obtain for debt with similar terms. Under the Amended Loan borrowing, the Company is required to repay the outstanding principal in 24 equal installments beginning 24 months after the date of the borrowing and is due in full in December 2018. The first tranche of the Amended Loan bears interest at a rate of 5.00% per annum. The Amended Loan carries prepayment penalties of 2.00% and 1.00% for prepayment within one and two years, respectively, and no prepayment penalty thereafter. In connection with the Amended Loan, the Company paid approximately $45,000 in third-party fees.

The Amended Loan results in a debt modification under ASC 470-50, Modifications and Extinguishments, as the change in present value of the remaining cash flows associated with the Original Loan and Amended Loan are not substantial.

As of December 31, 2014 and 2013, the net debt obligation was as follows (in thousands):

	December 31,
	2014			2013
Debt and unpaid accrued end-of term payment	$	5,003		$	5,042
Unamorized note discount		(80	)		(143	)

Net debt obligation	$	4,923		$	4,899

Future principal payments under the Amended Loan are as follows (in thousands):

Year ending December 31:
2015	$	—
2016		—
2017		2,437
2018		2,563

Total	$	5,000

The obligation at December 31, 2014 includes an end-of-term payment of $237,500, representing 4.75% of the total outstanding principal balance, which accretes over the life of the loan as interest expense. As a result of the debt discount and the end-of-term payment, the effective interest rate for the loan differs from the contractual rate.

Interest expense on the debt was as follows (in thousands):

	Year Ended December 31,
	2014		2013
Nominal interest	$	296	$	158
Amortization of debt discount		62		33
End-of-term payment interest		81		42

Total	$	439	$	233

Upon execution of the Original Loan, the Company issued the financial institution a warrant to purchase shares of Series C convertible preferred stock at $7.56 per share. At the time of issuance, the aggregate fair value of the warrant for the 24,801 shares exercisable under the warrant was $175,000. The fair value of the warrant was deducted from total proceeds, resulting in a debt discount to be amortized to interest expense over 48 months, through the maturity date of the Original Loan, using the effective interest rate method, and was recorded as a preferred stock warrant liability. The warrant was converted to a warrant to purchase the Company's common stock upon the completion of the Company's IPO. See Note 9.

The Company's obligations under the Amended Loan are secured by a security interest in substantially all of its assets, excluding its intellectual property and certain other assets. The Amended Loan contains customary conditions related to borrowing, events of default, and covenants, including covenants limiting the Company's ability to dispose of assets, undergo a change in control, merge with or acquire other entities, incur debt, incur liens, pay dividends or other distributions to holders of its capital stock, repurchase stock and make investments, in each case subject to certain exceptions. The Amended Loan also allows the lender to call the debt in the event there is a material adverse change in the Company's business or financial condition. The Company is required to be in compliance with a minimum liquidity or minimum revenue covenant. As of December 31, 2014, the Company was in compliance with the financial covenants.

Convertible Preferred Stock Warrant	12 Months Ended
Convertible Preferred Stock Warrant	Dec. 31, 2014
Convertible Preferred Stock Warrant
Convertible Preferred Stock Warrant	9. Convertible Preferred Stock Warrant In June 2013, in conjunction with the execution of the Original Loan, as discussed in Note 8, the Company issued to the lender a warrant to purchase up to 49,602 shares of Series C convertible preferred stock with an exercise price of $7.56 per share. Upon the draw-down of the $5.0 million term loan, the related warrant became exercisable for 24,801 shares. In November 2013, in connection with the Company's IPO, the warrant automatically became exercisable for 24,801 shares at an exercise price of $7.56 per share. The lender exercised the warrant with respect to 24,801 shares through a cashless exercise in March 2014, resulting in the issuance of 13,739 shares of the Company's common stock. The fair value of the then currently exercisable portion of the warrant in the amount of $175,000 was recorded as a preferred stock warrant liability upon issuance and was subject to re-measurement at each reporting period up to the closing date of the IPO when the Series C preferred stock converted into common stock. The fair value of the warrant upon issuance was calculated using the Black-Scholes option-pricing model with the following assumptions: Series C preferred stock value of $2.40 per share, contractual term of 7.3 years, risk-free interest rate of 2.1%, expected volatility of 73.7%, and expected dividend yield of 0%. Just prior to the closing of the IPO, the fair value of the warrant was approximately $261,000, and was calculated using the Black-Scholes option-pricing model with the following assumptions: Series C preferred stock value of $13.14 per share, contractual term of 7.0 years, risk-free interest rate of 2.0%, expected volatility of 81.4%, and expected dividend yield of 0%. The change in the fair value of approximately $86,000 was reported as an expense for the year ended December 31, 2013 and was included in other income (expense), net, in the statements of operations and comprehensive loss. The warrant was converted into a warrant to purchase common stock upon the completion of the IPO in 2013, and was reclassified to additional paid- in-capital in the Company's consolidated balance sheet.

Convertible Preferred Stock	12 Months Ended
Convertible Preferred Stock	Dec. 31, 2014
Convertible Preferred Stock
Convertible Preferred Stock	10. Convertible Preferred Stock In November 2012, the Company recorded a preferred stock liability as the investors received the right to purchase from the Company, on the same terms, additional shares of Series C convertible preferred stock, in a second tranche. As the investors held a majority of the board seats, the decision to complete the second tranche was deemed to be outside the control of the Company. The preferred stock liability was valued using the option-pricing method with the following assumptions: 100% probability of success of the second tranche, fair value of Series C preferred stock of $1.78, a term of 0.67 years and expected volatility of 44%. This resulted in an initial fair value of $0.9 million for the Company's obligation to sell the convertible preferred stock. At December 31, 2012, the Company revalued the preferred stock liability to $0.6 million, and recorded the $0.3 million valuation decrease to other income (expense), net, in the Company's statements of operations and comprehensive loss. In June 2013, the Company revalued the preferred stock liability to $2.7 million and recorded the $2.1 million valuation increase to other income (expense), net, in the Company's consolidated statements of operations and comprehensive loss. In June 2013, the $2.7 million liability was settled upon the issuance of the second tranche of Series C convertible preferred stock and was reclassified to additional paid-in-capital in the Company's consolidated balance sheets. On November 4, 2013, the Company completed its IPO. In connection with the IPO, the Company's 59,989,268 outstanding shares of convertible preferred stock were automatically converted into 14,997,312 shares of common stock.

Stockholders' Equity (Deficit)

12 Months Ended

Dec. 31, 2014

Stockholders' Equity

Stockholders' Equity

11. Stockholders' Equity

Common Stock

The Company's Restated Certificate of Incorporation authorizes the Company to issue 125,000,000 shares of common stock with a par value of $0.001 per share. The holder of each share of common stock shall have one vote for each share of stock. The common stockholders are also entitled to receive dividends whenever funds and assets are legally available and when declared by the Board of Directors, subject to the prior rights of holders of all series of convertible preferred stock outstanding. No dividends have been declared as of December 31, 2014.

As of December 31, 2014 and 2013, the Company had reserved shares of common stock for issuance as follows:

	December 31, 2014		December 31, 2013
Options issued and outstanding		3,249,469		2,359,287
Options available for grant under stock option plans		1,341,252		1,787,802
Common stock warrants issued and outstanding		—		24,801

Total		4,590,721		4,171,890

Preferred Stock

The Company's Restated Certificate of Incorporation authorizes the Company to issue 5,000,000 shares of preferred stock with a par value of $0.001 per share. No shares were issued and outstanding at December 31, 2014 or 2013.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Article 4

Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Stock Incentive Plans

12 Months Ended

Dec. 31, 2014

Stock Incentive Plans

Stock Incentive Plans

12. Stock Incentive Plans

Stock Option Plans

In February 15, 2008, the Company adopted the 2008 Stock Plan (the "2008 Plan"). The 2008 Plan provides for the granting of options to purchase common stock and common stock to employees, directors and consultants of the Company. The Company may grant incentive stock options ("ISOs"), non-statutory stock options ("NSOs") or restricted stock under the 2008 Plan. ISOs may only be granted to Company employees (including directors who are also considered employees). NSOs and restricted stock may be granted to Company employees, directors and consultants. Options may be granted for terms of up to ten years from the date of grant, as determined by the Board of Directors, provided however, that with respect to an ISO granted to a person who owns stock representing more than 10% of the voting power of all classes of stock of the Company, the term shall be for no more than five years from the date of grant. The exercise price of options granted must be at a price no less than 100% of the estimated fair value of the shares on the date of grant, as determined by the Board of Directors, provided however, that with respect to an ISO granted to an employee who at the time of grant of such option owns stock representing more than 10% of the voting power of all classes of stock of the Company, the exercise price shall not be less than 110% of the estimated fair value of the shares on the date of grant. Options granted to newly hired employees generally vest over four years (generally 25% after one year and monthly thereafter). Options granted to employees as part of annual bonus compensation are generally fully vested at the grant date.

On October 2, 2013, the Company adopted the 2013 Stock Incentive Plan (the "2013 Plan"). The 2013 Plan was subsequently approved by the Company's stockholders and became effective on November 4, 2013, immediately before the closing of the Company's IPO. Following the effectiveness of the 2013 Plan, no additional options will be granted under the 2008 Plan. An aggregate of 1,700,000 shares were initially reserved for issuance under the 2013 Plan. In addition, to the extent that any awards outstanding or subject to vesting restrictions under the 2008 Plan are subsequently forfeited or terminated for any reason before being exercised or settled, the shares of common stock reserved for issuance pursuant to such awards as of the closing of the IPO will become available for issuance under the 2013 Plan. The remaining shares available for grant under the 2008 Plan became available for issuance under the 2013 Plan upon the closing of the IPO. On the first day of each year from 2014 to 2023, the 2013 Plan authorizes an annual increase of the lesser of 4% of outstanding shares on the last day of the immediately preceding fiscal year or a lesser amount as determined by the Company's Board of Directors. As of December 31, 2014, 1,341,252 shares were available for future issuance under the 2013 Plan.

Pursuant to the 2013 Plan, stock options, restricted shares, stock units, including restricted stock units and stock appreciation rights may be granted to employees, consultants, and outside directors of the Company. Options granted may be either ISOs or NSOs.

Stock options are governed by stock option agreements between the Company and recipients of stock options. ISOs and NSOs may be granted under the 2013 Plan at an exercise price of not less than 100% of the fair market value of the common stock on the date of grant, determined by the Compensation Committee of the Board of Directors. Options become exercisable and expire as determined by the Compensation Committee, provided that the term of ISOs may not exceed ten years from the date of grant. Stock option agreements may provide for accelerated exercisability in the event of an optionee's death, disability, or retirement or other events.

Any outside director who was not previously an employee and who first joins the Company's Board of Directors on or after the effective date of the 2013 Plan will be automatically granted an initial NSO to purchase 35,000 shares of common stock upon first becoming a member of the Board of Directors. Twenty-five percent of the shares subject to the initial option will vest and become exercisable on the first anniversary of the date of grant. The balance (i.e. the remaining 75%) will vest and become exercisable over three years in equal monthly installments. On the first business day after each regularly scheduled annual meeting of stockholders, each outside director who was not elected to the Board of Directors for the first time at such meeting and who will continue serving as a member of the Board of Directors thereafter will be automatically granted an option to purchase 10,000 shares of common stock, provided that the outside director has served on the Board of Directors for at least six months. Each annual option will vest and become exercisable on the first anniversary of the date of grant, or immediately prior to the next regular annual meeting of the Company's stockholders following the date of grant if the meeting occurs prior to the first anniversary date. The options granted to outside directors will have a per share exercise price equal to 100% of the fair market value of the underlying shares on the date of grant and will become fully vested in the event of a change of control. In addition, such options will terminate on the earlier of (i) the day before the 10th anniversary of the date of grant or (ii) the date 12 months after the termination of the outside director's service for any reason.

The following table summarizes activity under the Company's stock option plans (aggregate intrinsic value in thousands):

	Shares Available for Grant			Stock Options Outstanding			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Balance—December 31, 2011		474,961			1,429,737		$	1.55		8.22	$	1,221
Additional options authorized		743,100			—
Granted		(931,944	)		931,944			2.78
Canceled		61,269			(61,269	)		1.97
Exercised		—			(72,743	)		1.05

Balance—December 31, 2012		347,386			2,227,669		$	2.06		8.17	$	4,311
Additional options authorized		1,950,000			—
Granted		(695,029	)		695,029			5.32
Canceled		185,445			(185,445	)		2.69
Exercised		—			(377,966	)		1.46

Balance—December 31, 2013		1,787,802			2,359,287		$	3.07		7.84	$	26,964
Additional options authorized		845,732			—
Granted		(1,488,492	)		1,488,492			13.38
Canceled		196,210			(196,210	)		9.37
Exercised		—			(402,100	)		1.68

Balance—December 31, 2014		1,341,252			3,249,469		$	7.59		7.88	$	12,400


Options vested and exercisable—December 31, 2014					1,370,944		$	2.92		6.44	$	9,287
Options vested and expected to vest—December 31, 2014					3,092,476		$	7.32		7.81	$	12,295

The aggregate intrinsic value was calculated as the difference between the exercise price of the options to purchase common stock and the fair market value of the Company's common stock, which was $9.66 per share as of December 31, 2014 and $14.50 per share as of December 31, 2013.

The weighted average fair value of options to purchase common stock granted was $9.08, $4.19 and $1.95 for the years ended December 31, 2014, 2013 and 2012, respectively.

The weighted average fair value of stock options vested was $3.07, $2.12 and $1.40 per share for the years ended December 31, 2014, 2013 and 2012, respectively. The aggregate estimated grant date fair value of employee options to purchase common stock vested during the years ended December 31, 2014 and 2013 was $1.6 million and $1.3 million, respectively.

The weighted-average fair value of stock options exercised was $1.18 and $0.97 for the years ended December 31, 2014 and 2013, respectively. The intrinsic value of stock options exercised was $3.2 million, $4.9 million and $0.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Stock-based Compensation

The following table summarizes stock-based compensation expense related to stock options for the years ended December 31, 2014, 2013 and 2012, and are included in the consolidated statements of operations and comprehensive loss as follows (in thousands):

	Year Ended December 31,
	2014		2013		2012
Cost of revenue	$	51	$	34	$	26
Research and development		790		250		131
Selling and marketing		707		169		111
General and administrative		2,000		794		407

Total stock-based compensation expense	$	3,548	$	1,247	$	675

As of December 31, 2014, the Company had $9.9 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over an estimated weighted-average period of 3.0 years.

The estimated grant-date fair value of employee stock options was calculated using the Black-Scholes option-pricing model, based on the following assumptions:

	Year Ended December 31,
	2014	2013	2012
Weighted-average volatility	70.19 - 78.54%	80.42 - 81.41%	82.07 - 84.33%
Weighted-average expected term (years)	5.50 - 6.08	5.00 - 6.08	5.00 - 6.08
Risk-free interest rate	1.66 - 2.04%	0.88 - 2.11%	0.65 - 1.19%
Expected dividend yield	—	—	—

The estimated grant-date fair value of non-employee stock options was calculated using the Black-Scholes option-pricing model, based on the following assumptions:

	Year Ended December 31,
	2014	2013	2012
Weighted-average volatility	73.20 - 74.48%	77.86 - 78.14%	81.14 - 82.11%
Weighted-average expected term (years)	8.75 - 10.00	7.72 - 9.75	8.23 - 9.93
Risk-free interest rate	2.09 - 2.20%	2.59 - 2.99%	1.43 - 1.77%
Expected dividend yield	—	—	—

Equity-based Compensation

In February 2013, the Company's Board of Directors authorized the grant of 100,498 fully vested stock options at a fair value of $2.59, determined using the Black-Scholes option-pricing valuation model, resulting in a $259,000 expense in the year ended December 31, 2012. Upon issuance of the options, the accrued liability was reclassified into additional paid-in capital. For the years ended December 31, 2014 and 2013, the Company paid executive bonuses only in the form of cash.

Genzyme Co-promotion Agreement	12 Months Ended
Genzyme Co-promotion Agreement	Dec. 31, 2014
Genzyme Co-promotion Agreement
Genzyme Co-promotion Agreement	13. Genzyme Co-Promotion Agreement In January 2012, the Company and Genzyme Corporation ("Genzyme") executed a co-promotion agreement for the co-exclusive rights and license to promote and market the Company's Afirma thyroid diagnostic solution in the United States and in 40 named countries. In exchange, the Company received a $10.0 million upfront co-promotion fee from Genzyme in February 2012. Under the terms of the agreement, Genzyme will receive a percentage of U.S. cash receipts that the Company has received related to Afirma as co-promotion fees. The percentage was 50% in 2012, 40% from January 2013 through February 2014, and 32% beginning in February 2014. Genzyme's obligation to also spend up to $500,000 for qualifying clinical development activities in countries that require additional testing for approval expired in July 2014. On August 12, 2014, the Company signed a binding Letter of Agreement with Genzyme to amend terms of the co-promotion agreement. On November 7, 2014, the Company signed an Amended and Restated U.S. Co-Promotion Agreement ("Amended Agreement") with Genzyme. Under the Amended Agreement, the co-promotion fees Genzyme will receive as a percentage of U.S. cash receipts were reduced from 32% to 15% beginning January 1, 2015. Through August 11, 2014, the Company amortized the $10.0 million upfront co-promotion fee over a four-year period, which was management's best estimate of the life of the agreement, in part because after that period either party could have terminated the agreement without penalty. Effective August 12, 2014, the Company extended the amortization period from January 2016 to June 2016, the modified earliest period either party could terminate the agreement without penalty. The Company accounted for the change in accounting estimate prospectively. Either party may terminate the agreement with six months prior notice, however, under the Amended Agreement, neither party can terminate the agreement for convenience prior to June 30, 2016. The agreement with Genzyme expires in 2027. On November 7, 2014, the Company signed a binding Letter of Agreement (the "LOA") with Genzyme to negotiate a potential co-promotion agreement to promote Afirma GEC in countries other than the United States. The LOA provided an exclusive negotiation period to attempt to negotiate in good faith until December 12, 2014 a mutually agreeable co-promotion agreement ("Ex-U.S. Co-Promotion Agreement") pursuant to which the companies could co-promote the test in six initial countries. During such exclusive negotiation period, both parties were prohibited from negotiating with any third party with respect to those six countries. On December 12, 2014 the parties amended the LOA to extend the exclusive negotiation period from December 12, 2014 to January 31, 2015. During the extended period, the terms of the original co-promotion agreement with respect to countries outside the U.S. would remain in effect, including the payment to Genzyme of 32% of net revenues received by the Company on the test in countries outside the U.S. On January 30, 2015 the parties further amended the LOA to extend the exclusive negotiation period to February 14, 2015. On February 13, 2015, the Company signed an Ex-U.S. Co-Promotion Agreement with Genzyme for the promotion of the Afirma GEC test with exclusivity in five countries outside the United States initially and in other countries agreed to from time to time. See Note 18, Subsequent Event. The Company incurred $12.0 million, $8.6 million and $5.5 million in co-promotion expense in the years ended December 31, 2014, 2013 and 2012, respectively, which is included in selling and marketing expenses in the consolidated statements of operations and comprehensive loss. The Company's outstanding obligation to Genzyme totaled $6.0 million and $6.7 million at December 31, 2014 and December 31, 2013, respectively. Of the $6.0 million obligation at December 31, 2014, $2.7 million is included in accounts payable and $3.3 million is included in accrued liabilities in the Company's consolidated balance sheets. Of the $6.7 million obligation at December 31, 2013, $1.8 million is included in accounts payable and $4.9 million is included in accrued liabilities in the Company's consolidated balance sheets. The Company amortized $2.3 million, $2.5 million and $2.4 million of the $10.0 million up-front co-promotion fee in the years ended December 31, 2014, 2013 and 2012, respectively, which is reflected as a reduction to selling and marketing expenses in the consolidated statements of operations and comprehensive loss.

Thyroid Cytopathology Partners	12 Months Ended
Thyroid Cytopathology Partners	Dec. 31, 2014
Thyroid Cytopathology Partners.
Thyroid Cytopathology Partners	14. Thyroid Cytopathology Partners In 2010, the Company entered into an arrangement with Pathology Resource Consultants, P.A. ("PRC") to set up and manage a specialized pathology practice to provide testing services to the Company. There is no direct monetary compensation from the Company to PRC as a result of this arrangement. The Company's service agreement is with the specialized pathology practice, Thyroid Cytopathology Partners, ("TCP"), and is effective through December 31, 2015, and thereafter automatically renews every year unless either party provides notice of intent not to renew at least 12 months prior to the end of the then-current term. Under the service agreement, the Company pays TCP based on a fixed price per test schedule, which is reviewed periodically for changes in market pricing. Subsequent to December 2012, an amendment to the service agreement allows TCP to use a portion of the Company's facility in Austin, Texas. The Company does not have an ownership interest in or provide any form of financial or other support to TCP. The Company has concluded that TCP represents a variable interest entity and that the Company is not the primary beneficiary as it does not have the ability to direct the activities that most significantly impact TCP's economic performance. Therefore, the Company does not consolidate TCP. All amounts paid to TCP under the service agreement are expensed as incurred and included in cost of revenue in the consolidated statements of operations and comprehensive loss. The Company incurred $4.0 million, $3.2 million and $1.8 million in the years ended December 31, 2014, 2013 and 2012, respectively, in cytopathology testing and evaluation services expenses with TCP. The Company's outstanding obligations to TCP for cytopathology testing services were $1.1 million and $0.6 million as of December 31, 2014 and 2013, respectively, and are included in accounts payable in the Company's consolidated balance sheets. TCP reimburses the Company for a proportionate share of the Company's rent and related operating expense costs for the leased facility. TCP's portion of rent and related operating expense costs for the shared space at the Austin, Texas facility was $86,000 and $49,000 for the years ended December 31, 2014 and 2013. TCP reimbursed the Company $59,000 in 2013 and the resulting excess payment of $10,000 was included in accounts payable in the Company's consolidated balance sheets at December 31, 2013.

Income Taxes

12 Months Ended

Dec. 31, 2014

Income Taxes

Income Taxes

15. Income Taxes

The Company generated a pretax loss of $29.4 million, $25.6 million and $18.6 million in the United States for the years ended December 31, 2014, 2013 and 2012, respectively. Since inception, the Company has not generated any pretax income or loss outside of the United States. The Company did not record a provision or benefit for income taxes during the years ended December 31, 2014, 2013 and 2012.

The Company follows FASB ASC No. 740, Income Taxes for the Computation and Presentation of its Tax Provision. The following table presents a reconciliation of the tax expense computed at the statutory federal rate and the Company's tax expense for the period presented (in thousands):

	Year Ended December, 31,
	2014			2013			2012
U.S. federal taxes at statutory rate	$	(9,987	)	$	(8,697	)	$	(6,341	)
State tax (net of federal benefit)		5			11			(1,074	)
Permanent differences		64			790			(23	)
Incentive stock options		672			355			284
Tax credits		(461	)		(502	)		(113	)
Change in valuation allowance		9,707			8,043			7,267

Total	$	—		$	—		$	—

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands):

	Year Ended December 31,
	2014			2013			2012
Current deferred tax assets:
Genzyme co-promotion agreement	$	793		$	1,005		$	1,001
Accruals and deferred rent		1,819			599			148

Gross deferred tax assets		2,612			1,604			1,149
Valuation allowance		(2,312	)		(1,603	)		(1,145	)

Net deferred tax assets		300			1			4

Non-current deferred tax assets:
Net operating loss carryforwards		41,971			28,569			20,536
Research and development credits		1,916			1,455			954
Stock-based compensation		826			313			154
Genzyme co-promotion agreement		202			787			2,048
Accruals, deferred rent and other		1,562			106			9

Gross deferred tax assets		46,477			31,230			23,701
Valuation allowance		(41,127	)		(31,216	)		(23,622	)

Net deferred tax assets		5,350			14			79

Deferred tax liabilities:
Property and equipment		(60	)		(15	)		(83	)
In-process research and development		(5,590	)		—			—

Gross deferred tax liabilities		(5,650	)		(15	)		(83	)

Net non-current deferred tax liabilities		(300	)		(1	)		(4	)

Total deferred tax assets	$	—		$	—		$	—

The Company has established a full valuation allowance against its net deferred tax assets due to the uncertainty surrounding realization of such assets. The valuation allowance increased $10.6 million and $8.1 million during the years ended December 31, 2014 and 2013, respectively.

As of December 31, 2014, the Company had net operating loss carryforwards of approximately $113.6 million and $60.6 million available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. Of these amounts, $0.2 million represent federal and state deductions from stock-based compensation, which will be recorded as an adjustment to additional paid-in capital when they reduce tax payable. The U.S. federal net operating loss carryforwards will begin to expire in 2026 while for state purposes, the net operating losses will begin to expire in 2018.

As of December 31, 2014, the Company had net credit carryforwards of approximately $2.2 million and $1.6 million available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. The federal credit carryforwards begin to expire in 2028. California credits have no expiration date.

The Internal Revenue Code of 1986, as amended, imposes restrictions on the utilization of net operating losses and tax credits in the event of an "ownership change" of a corporation. Accordingly, a company's ability to use net operating losses and tax credits may be limited as prescribed under Internal Revenue Code Section 382 and 383 ("IRC Section 382"). Events which may cause limitations in the amount of the net operating losses or tax credits that the Company may use in any one year include, but are not limited to, a cumulative ownership change of more than 50% over a three-year period. Utilization of the federal and state net operating losses may be subject to substantial annual limitation due to the ownership change limitations provided by the IRC Section 382 rules and similar state provisions. In the event the Company has any changes in ownership, net operating losses and research and development credit carryovers could be limited and may expire unutilized.

Uncertain Tax Positions

As of December 31, 2014, the Company had unrecognized tax benefits of $1.6 million, none of which would currently affect the Company's effective tax rate if recognized due to the Company's deferred tax assets being fully offset by a valuation allowance. The Company does not anticipate that the amount of unrecognized tax benefits relating to tax positions existing at December 31, 2014 will significantly increase or decrease within the next 12 months.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	Year Ended December 31,
	2014		2013		2012
Unrecognized tax benefits, beginning of period	$	727	$	481	$	341
Gross increases—tax position in prior period		548		68		67
Gross increases—current period tax positions		296		178		73

Unrecognized tax benefits, end of period	$	1,571	$	727	$	481

It is the Company's policy to include penalties and interest expense related to income taxes as a component of other income (expense), net, and interest expense, respectively, as necessary. There was no interest expense or penalties related to unrecognized tax benefits recorded through December 31, 2014.

The Company's major tax jurisdictions are the United States and California. All of the Company's tax years will remain open for examination by the Federal and state tax authorities for three and four years, respectively, from the date of utilization of the net operating loss or research and development credit. The Company does not have any tax audits pending.

401(k) Plan	12 Months Ended
401(k) Plan	Dec. 31, 2014
401(k) Plan
401(k) Plan	16. 401(k) Plan The Company sponsors a 401(k) defined contribution plan covering all employees. There were no employer contributions to the plan in the years ended December 31, 2014 and 2013.

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2014

Selected Quarterly Financial Data (Unaudited)

Selected Quarterly Financial Data (Unaudited)

17. Selected Quarterly Financial Data (Unaudited)

The following table presents selected unaudited consolidated financial data for each of the eight quarters in the two-year period ended December 31, 2014. The Company believes this information reflects all recurring adjustments necessary to fairly present this information when read in conjunction with the Company's financial statements and the related notes. Net loss per common share, basic and diluted, for the four quarters of each fiscal year may not sum to the total for the fiscal year because of the different number of shares outstanding during each period. The results of operations for any quarter are not necessarily indicative of the results to be expected for any future period.

Quarter Ended	March 31			June 30			September 30			December 31
	(In thousands, except share and per share data)
2014:
Total revenues	$	7,476		$	8,677		$	9,838		$	12,199
Net loss		(6,674	)		(6,655	)		(7,902	)		(8,142	)
Net loss per common share, basic and diluted		(0.32	)		(0.31	)		(0.37	)		(0.36	)
Shares used to compute net loss per common share, basic and diluted		21,148,342			21,237,196			21,648,660			22,508,250
2013:
Total revenues	$	4,384		$	5,068		$	5,594		$	6,838
Net loss		(6,895	)		(6,490	)		(6,303	)		(5,892	)
Net loss per common share, basic and diluted		(9.04	)		(7.53	)		(6.59	)		(0.42	)
Shares used to compute net loss per common share, basic and diluted		763,021			861,839			955,890			13,944,239

Subsequent Event	12 Months Ended
Subsequent Event	Dec. 31, 2014
Subsequent Event.
Subsequent Event	18. Subsequent Event (Unaudited) On February 13, 2015, the Company signed an Ex-U.S. Co-Promotion Agreement with Genzyme for the promotion of the Afirma GEC test with exclusivity in five countries outside the United States initially and in other countries agreed to from time to time. The term of the agreement is January 1, 2015 and continuing until December 31, 2019 with extension of the agreement possible upon agreement of the parties. Country specific terms have been established under this agreement for Brazil and Singapore and a right of first negotiation has been established for Canada, the Netherlands and Italy. The Company will pay Genzyme 25% of net revenue in Brazil and Singapore over a five-year period commencing January 1, 2015. Beginning in the fourth year of the agreement, if the Company terminates the agreement for convenience, the Company may be required to pay a termination fee contingent on the number of GEC billable results generated.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2014

Summary of Significant Accounting Policies

Basis of Presentation

Use of Estimates

Liquidity

Concentrations of Credit Risk and Other Risks and Uncertainties

	Year Ended December 31,
	2014			2013			2012
Medicare		26	%		32	%		34	%
Aetna		11	%		9	%		13	%
United Healthcare		18	%		18	%		12	%

		55	%		59	%		59	%

The Company's significant third-party payers and their related accounts receivable balance at December 31, 2014 and 2013 as a percentage of total accounts receivable are as follows:

	December 31,
	2014			2013
Medicare		64	%		78	%
Aetna		12	%		—
United Healthcare		14	%		3	%

No other third-party payer represented more than 10% of the Company's accounts receivable balances for these periods.

Cash Equivalents

Restricted Cash

Allowance for Doubtful Accounts

The balance of allowance for doubtful accounts as of December 31, 2014 and 2013, including charges to bad debt expense and write-offs, net of recoveries, was as follows:

	As of December 31,
	2014			2013
	(In thousands)
Beginning balance	$	107		$	222
Charged to expense		54			109
Write-offs, net of recoveries		(77	)		(224	)

Ending balance	$	84		$	107

Supplies Inventory

Property and Equipment

Internal-use Software

Business Combination

Goodwill

Intangible Assets

Impairment of Long-lived Assets

Bonus Accruals

Fair Value of Financial Instruments

Revenue Recognition

Cost of Revenue

Research and Development

Income Taxes

Stock-based Compensation

Equity awards issued to non-employees are valued using the Black-Scholes option-pricing model and are subject to re-measurement as the underlying equity awards vest.

Net Loss per Common Share

Recent Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Summary of Significant Accounting Policies

Schedule of balance of allowance for doubtful accounts, including charges to bad debt expense and write-offs, net of recoveries

	As of December 31,
	2014			2013
	(In thousands)
Beginning balance	$	107		$	222
Charged to expense		54			109
Write-offs, net of recoveries		(77	)		(224	)

Ending balance	$	84		$	107

Revenue concentration risk | Revenue

Summary of Significant Accounting Policies

Schedule of the Company's third-party payers as a percentage of total

	Year Ended December 31,
	2014			2013			2012
Medicare		26	%		32	%		34	%
Aetna		11	%		9	%		13	%
United Healthcare		18	%		18	%		12	%

		55	%		59	%		59	%

Gross receivables concentration risk | Accounts receivable

Summary of Significant Accounting Policies

Schedule of the Company's third-party payers as a percentage of total

	December 31,
	2014			2013
Medicare		64	%		78	%
Aetna		12	%		—
United Healthcare		14	%		3	%

Net Loss Per Common Share (Tables)

12 Months Ended

Dec. 31, 2014

Net Loss Per Common Share

Schedule of the calculation of basic and diluted net loss per common share

The following table presents the calculation of basic and diluted net loss per common share for the years ended December 31, 2014, 2013 and 2012 (in thousands, except share and per share amounts):

	Year Ended December 31,
	2014			2013			2012
Net loss	$	(29,373	)	$	(25,580	)	$	(18,649	)


Shares used to compute net loss per common share, basic and diluted		21,639,374			4,158,664			650,333


Net loss per common share, basic and diluted	$	(1.36	)	$	(6.15	)	$	(28.68	)

Schedule of outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share

	Year Ended December 31,
	2014		2013
Shares of common stock subject to outstanding options		3,249,469		2,359,287
Shares of common stock issuable upon exercise of warrants		—		24,801

Total shares of common stock equivalents		3,249,469		2,384,088

Business Combination (Tables)

12 Months Ended

Dec. 31, 2014

Business Combination

Schedule of pro forma financial information as if the Merger had occurred as of January1, 2013

	Year Ended December 31,
	2014			2013
Revenue	$	38,190		$	21,884


Net loss	$	(29,090	)	$	(28,605	)

Allegro

Business Combination

Schedule of acquisition consideration

The acquisition consideration was comprised of (in thousands):

Stock	$	10,078
Cash		2,725
Payment of outstanding indebtedness		4,290

Total acquisition consideration	$	17,093

Schedule of fair value of assets acquired and liabilities assumed

The fair value of the assets acquired and liabilities assumed at the closing date of the Merger are summarized below (in thousands):

Cash and cash equivalents	$	29
Prepaid expenses		3
Other current assets		13
In-process research and development ("IPR&D")		16,000
Goodwill		1,057
Accrued liabilities		(9	)

Total net assets acquired	$	17,093

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2014

Balance Sheet Components

Schedule of property and equipment

Property and equipment consisted of the following (in thousands):

	Year Ended December 31,
	2014			2013
Leasehold improvements	$	788		$	779
Laboratory equipment		4,199			2,946
Computer equipment		875			645
Software, including software developed for internal use		1,353			901
Furniture and fixtures		197			189
Construction-in-process		739			307

Total property and equipment, at cost		8,151			5,767
Accumulated depreciation and amortization		(3,990	)		(2,815	)

Total property and equipment, net	$	4,161		$	2,952

Schedule of depreciation and amortization expense recorded in the statements of operations and comprehensive loss

	Year Ended December 31,
	2014		2013		2012
Cost of revenue	$	677	$	593	$	401
Research and development		187		179		184
Selling and marketing		101		54		46
General and administrative		210		173		75

Total depreciation and amortization expense	$	1,175	$	999	$	706

Schedule of accrued liabilities

Accrued liabilities consisted of the following (in thousands):

	Year Ended December 31,
	2014		2013
Accrued compensation expenses	$	2,673	$	1,962
Accrued Genzyme co-promotion fees		3,309		4,915
Accrued other		1,869		717

Total accrued liabilities	$	7,851	$	7,594

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Measurements

Summary of the changes in the fair value of the Company's Level 3 financial liabilities, which are measured on a recurring basis

The following table sets forth the changes in the fair value of the Company's Level III financial liabilities, which consisted of a preferred stock liability during 2013, which were measured on a recurring basis (in thousands):

	December 31,
	2014		2013
Beginning balance	$	—	$	583
Change in fair value of preferred stock liability recorded as other expense, net		—		2,070
Settlement of preferred stock liability		—		(2,653	)
Fair value of preferred stock warrant liability		—		175
Change in fair value of preferred stock warrant liability recorded as other expense, net		—		86
Conversion of preferred stock warrant liability		—		(261	)

Ending balance	$	—	$	—

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies

Schedule of future minimum lease payments under non-cancelable operating leases

Future minimum lease payments under non-cancelable operating leases as of December 31, 2014 are as follows (in thousands):

Year Ending December 31,	Amounts
2015	$	989
2016		413
2017		222
2018		130
Thereafter		—

Total minimum lease payments	$	1,754

Debt (Tables)

12 Months Ended

Dec. 31, 2014

Debt

Schedule of net debt obligation

As of December 31, 2014 and 2013, the net debt obligation was as follows (in thousands):

	December 31,
	2014			2013
Debt and unpaid accrued end-of term payment	$	5,003		$	5,042
Unamorized note discount		(80	)		(143	)

Net debt obligation	$	4,923		$	4,899

Schedule of future principal payments under the Amended Loan

Future principal payments under the Amended Loan are as follows (in thousands):

Year ending December 31:
2015	$	—
2016		—
2017		2,437
2018		2,563

Total	$	5,000

Schedule of interest expense on debt

Interest expense on the debt was as follows (in thousands):

	Year Ended December 31,
	2014		2013
Nominal interest	$	296	$	158
Amortization of debt discount		62		33
End-of-term payment interest		81		42

Total	$	439	$	233

Stockholders' Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2014

Stockholders' Equity

Schedule of reserved shares of common stock for issuance

	December 31, 2014		December 31, 2013
Options issued and outstanding		3,249,469		2,359,287
Options available for grant under stock option plans		1,341,252		1,787,802
Common stock warrants issued and outstanding		—		24,801

Total		4,590,721		4,171,890

Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2014

Stock incentive plans

Summary of activity under the Company's stock option plans

The following table summarizes activity under the Company's stock option plans (aggregate intrinsic value in thousands):

	Shares Available for Grant			Stock Options Outstanding			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Balance—December 31, 2011		474,961			1,429,737		$	1.55		8.22	$	1,221
Additional options authorized		743,100			—
Granted		(931,944	)		931,944			2.78
Canceled		61,269			(61,269	)		1.97
Exercised		—			(72,743	)		1.05

Balance—December 31, 2012		347,386			2,227,669		$	2.06		8.17	$	4,311
Additional options authorized		1,950,000			—
Granted		(695,029	)		695,029			5.32
Canceled		185,445			(185,445	)		2.69
Exercised		—			(377,966	)		1.46

Balance—December 31, 2013		1,787,802			2,359,287		$	3.07		7.84	$	26,964
Additional options authorized		845,732			—
Granted		(1,488,492	)		1,488,492			13.38
Canceled		196,210			(196,210	)		9.37
Exercised		—			(402,100	)		1.68

Balance—December 31, 2014		1,341,252			3,249,469		$	7.59		7.88	$	12,400


Options vested and exercisable—December 31, 2014					1,370,944		$	2.92		6.44	$	9,287
Options vested and expected to vest—December 31, 2014					3,092,476		$	7.32		7.81	$	12,295

Stock-based Compensation

Stock incentive plans

Summary of share-based compensation expense

	Year Ended December 31,
	2014		2013		2012
Cost of revenue	$	51	$	34	$	26
Research and development		790		250		131
Selling and marketing		707		169		111
General and administrative		2,000		794		407

Total stock-based compensation expense	$	3,548	$	1,247	$	675

Stock-based Compensation, employees

Stock incentive plans

Schedule of assumptions used to calculate estimated grant date fair value of stock options using the Black-Scholes option-pricing valuation model

	Year Ended December 31,
	2014	2013	2012
Weighted-average volatility	70.19 - 78.54%	80.42 - 81.41%	82.07 - 84.33%
Weighted-average expected term (years)	5.50 - 6.08	5.00 - 6.08	5.00 - 6.08
Risk-free interest rate	1.66 - 2.04%	0.88 - 2.11%	0.65 - 1.19%
Expected dividend yield	—	—	—

Stock-based Compensation, non-employees

Stock incentive plans

Schedule of assumptions used to calculate estimated grant date fair value of stock options using the Black-Scholes option-pricing valuation model

	Year Ended December 31,
	2014	2013	2012
Weighted-average volatility	73.20 - 74.48%	77.86 - 78.14%	81.14 - 82.11%
Weighted-average expected term (years)	8.75 - 10.00	7.72 - 9.75	8.23 - 9.93
Risk-free interest rate	2.09 - 2.20%	2.59 - 2.99%	1.43 - 1.77%
Expected dividend yield	—	—	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Taxes

Schedule of reconciliation of tax expense computed at the statutory federal rate and the Company's tax expense

The following table presents a reconciliation of the tax expense computed at the statutory federal rate and the Company's tax expense for the period presented (in thousands):

	Year Ended December, 31,
	2014			2013			2012
U.S. federal taxes at statutory rate	$	(9,987	)	$	(8,697	)	$	(6,341	)
State tax (net of federal benefit)		5			11			(1,074	)
Permanent differences		64			790			(23	)
Incentive stock options		672			355			284
Tax credits		(461	)		(502	)		(113	)
Change in valuation allowance		9,707			8,043			7,267

Total	$	—		$	—		$	—

Schedule of significant components of the Company's deferred tax assets and liabilities

Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands):

	Year Ended December 31,
	2014			2013			2012
Current deferred tax assets:
Genzyme co-promotion agreement	$	793		$	1,005		$	1,001
Accruals and deferred rent		1,819			599			148

Gross deferred tax assets		2,612			1,604			1,149
Valuation allowance		(2,312	)		(1,603	)		(1,145	)

Net deferred tax assets		300			1			4

Non-current deferred tax assets:
Net operating loss carryforwards		41,971			28,569			20,536
Research and development credits		1,916			1,455			954
Stock-based compensation		826			313			154
Genzyme co-promotion agreement		202			787			2,048
Accruals, deferred rent and other		1,562			106			9

Gross deferred tax assets		46,477			31,230			23,701
Valuation allowance		(41,127	)		(31,216	)		(23,622	)

Net deferred tax assets		5,350			14			79

Deferred tax liabilities:
Property and equipment		(60	)		(15	)		(83	)
In-process research and development		(5,590	)		—			—

Gross deferred tax liabilities		(5,650	)		(15	)		(83	)

Net non-current deferred tax liabilities		(300	)		(1	)		(4	)

Total deferred tax assets	$	—		$	—		$	—

Schedule of reconciliation of the beginning and ending amount of unrecognized tax benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	Year Ended December 31,
	2014		2013		2012
Unrecognized tax benefits, beginning of period	$	727	$	481	$	341
Gross increases—tax position in prior period		548		68		67
Gross increases—current period tax positions		296		178		73

Unrecognized tax benefits, end of period	$	1,571	$	727	$	481

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2014

Selected Quarterly Financial Data (Unaudited)

Schedule of selected quarterly financial data (unaudited)

Quarter Ended	March 31			June 30			September 30			December 31
	(In thousands, except share and per share data)
2014:
Total revenues	$	7,476		$	8,677		$	9,838		$	12,199
Net loss		(6,674	)		(6,655	)		(7,902	)		(8,142	)
Net loss per common share, basic and diluted		(0.32	)		(0.31	)		(0.37	)		(0.36	)
Shares used to compute net loss per common share, basic and diluted		21,148,342			21,237,196			21,648,660			22,508,250
2013:
Total revenues	$	4,384		$	5,068		$	5,594		$	6,838
Net loss		(6,895	)		(6,490	)		(6,303	)		(5,892	)
Net loss per common share, basic and diluted		(9.04	)		(7.53	)		(6.59	)		(0.42	)
Shares used to compute net loss per common share, basic and diluted		763,021			861,839			955,890			13,944,239

Organization and Description of Business (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Nov. 04, 2013 USD ($) $ / shares shares	Dec. 31, 2014 item $ / shares	Dec. 31, 2013 $ / shares shares
Organization and Description of Business
Number of patients who undergo bronchoscopy in the United States each year \| item		250,000
Initial Public Offering
Net proceeds from issuance of common stock in IPO	$ 59.2
Underwriting discounts and commissions	4.6
Offering expenses	$ 2.5
Common Stock
Initial Public Offering
Number of shares issued and sold in IPO \| shares	5,100,351		5,100,351
Issuance price per share in IPO (in dollars per share) \| $ / shares	$ 13.00	$ 9.66	$ 14.50
Common stock issued on automatic conversion of outstanding convertible preferred stock (in shares) \| shares	14,997,312		14,997,312

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2014 USD ($) Institution	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)
Liquidity
Accumulated deficit	$ (115,022)	$ (85,649)
Cash and cash equivalents	$ 35,014	71,220	$ 14,002	$ 7,566
Concentrations of Credit Risk and Other Risks and Uncertainties
Number of major financial institutions with which the company's cash and cash equivalents are deposited \| Institution	1
Restricted Cash
Cash reserved to cover liabilities associated with Merger	$ 70
Long term deposit consisting of letter of credit serving as security for lease	118	118
Activity of allowance for doubtful accounts
Beginning balance	107	222
Charged to expense	54	109	225
Write-offs, net of recoveries	(77)	(224)
Ending balance	$ 84	$ 107	$ 222
Revenue \| Revenue concentration risk
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	55.00%	59.00%	59.00%
Revenue \| Revenue concentration risk \| Medicare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	26.00%	32.00%	34.00%
Revenue \| Revenue concentration risk \| Aetna
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	11.00%	9.00%	13.00%
Revenue \| Revenue concentration risk \| United Healthcare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	18.00%	18.00%	12.00%
Accounts receivable \| Gross receivables concentration risk \| Medicare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	64.00%	78.00%
Accounts receivable \| Gross receivables concentration risk \| Aetna
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	12.00%
Accounts receivable \| Gross receivables concentration risk \| United Healthcare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	14.00%	3.00%

Summary of Significant Accounting Policies (Details 2) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Internal-use Software
Total cost	$ 8,151,000	$ 5,767,000
Accumulated depreciation	3,990,000	2,815,000
Net book value	$ 4,161,000	2,952,000
Minimum
Property and Equipment and Internal-use Software
Estimated useful life	3 years
Maximum
Property and Equipment and Internal-use Software
Estimated useful life	5 years
Capitalized software
Property and Equipment and Internal-use Software
Estimated useful life	3 years
Internal-use Software
Total cost	$ 927,000	482,000
Accumulated depreciation	330,000	195,000
Net book value	597,000	287,000
Capitalized costs	445,000	212,000
Amortization expense	$ 135,000	$ 108,000	$ 47,000

Summary of Significant Accounting Policies (Details 3) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Asset impairment
Goodwill impairment	$ 0
Indefinite lived assets, other than goodwill, impairment	0
Long-lived asset impairment	0	$ 0
Bonus Accruals
Accrued liabilities associated with employee and executive bonus plans	1,100,000	1,100,000
Revenue Recognition
Revenue recognized when cash is received	25,700,000	14,600,000	$ 7,500,000
Revenue recognized on accrual basis	$ 12,500,000	$ 7,300,000	$ 4,100,000

Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Calculation of basic and diluted net loss per common share
Net loss	$ (8,142)	$ (7,902)	$ (6,655)	$ (6,674)	$ (5,892)	$ (6,303)	$ (6,490)	$ (6,895)	$ (29,373)	$ (25,580)	$ (18,649)
Shares used to compute net loss per common share, basic and diluted (in shares)	22,508,250	21,648,660	21,237,196	21,148,342	13,944,239	955,890	861,839	763,021	21,639,374	4,158,664	650,333
Net loss per common share, basic and diluted (in dollars per share)	$ (0.36)	$ (0.37)	$ (0.31)	$ (0.32)	$ (0.42)	$ (6.59)	$ (7.53)	$ (9.04)	$ (1.36)	$ (6.15)	$ (28.68)
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Total shares of common stock equivalents (in shares)									3,249,469	2,384,088
Options
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Total shares of common stock equivalents (in shares)									3,249,469	2,359,287
Common Stock Warrants
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Total shares of common stock equivalents (in shares)										24,801

Business Combination (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 16, 2014	Dec. 31, 2014	Dec. 31, 2013
Fair value of the assets acquired and liabilities assumed:
Goodwill		$ 1,057
Pro-Forma Financial Information
Revenue		38,190	$ 21,884
Net loss		(29,090)	(28,605)
Allegro
Business Acquisition [Line Items]
Number of Allegro shares received for each share of common stock issued and outstanding of a wholly-owned subsidiary of the Company	1
Conversion right, number of shares	964,377
Conversion right, cash	$ 2,700
Outstanding indebtedness settled in cash	4,300
Acquisition-related costs	500
Transaction bonuses and severance payments	1,200
Acquisition consideration
Stock	10,078
Cash	2,725
Payment of outstanding indebtedness	4,290
Total acquisition consideration	$ 17,093
Closing price of Company's common stock	$ 10.45
Fair value of the assets acquired and liabilities assumed:
Cash and cash equivalents	$ 29
Prepaid expenses	3
Other current assets	13
In-process research and development	16,000
Goodwill	1,057
Accrued liabilities	(9)
Total net assets acquired	$ 17,093
Discount rate (as a percent)	18.50%
Allegro \| Transaction bonus and other payments to employees and acquisition related costs
Pro-Forma Financial Information
Net loss		2,200
Allegro \| Interest expense related to indebtedness of acquired entity
Pro-Forma Financial Information
Net loss		$ 2,300	$ 4,500
Allegro \| IPR&D \| Maximum
Fair value of the assets acquired and liabilities assumed:
Useful life	20 years

Balance Sheet Components (Details) - USD ($) $ in Thousands	12 Months Ended
Balance Sheet Components (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and Equipment, Net
Total property and equipment, at cost	$ 8,151	$ 5,767
Accumulated depreciation and amortization	(3,990)	(2,815)
Total property and equipment, net	4,161	2,952
Depreciation and amortization expense	1,175	999	$ 706
Cost of revenue
Property and Equipment, Net
Depreciation and amortization expense	677	593	401
Research and development
Property and Equipment, Net
Depreciation and amortization expense	187	179	184
Selling and marketing
Property and Equipment, Net
Depreciation and amortization expense	101	54	46
General and administrative
Property and Equipment, Net
Depreciation and amortization expense	210	173	$ 75
Leasehold improvements
Property and Equipment, Net
Total property and equipment, at cost	788	779
Laboratory equipment
Property and Equipment, Net
Total property and equipment, at cost	4,199	2,946
Computer equipment
Property and Equipment, Net
Total property and equipment, at cost	875	645
Software, including software developed for internal use
Property and Equipment, Net
Total property and equipment, at cost	1,353	901
Furniture and fixtures
Property and Equipment, Net
Total property and equipment, at cost	197	189
Construction-in-process
Property and Equipment, Net
Total property and equipment, at cost	$ 739	$ 307

Balance Sheet Components (Details 2) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Accrued Liabilities
Accrued compensation expenses	$ 2,673	$ 1,962
Accrued Genzyme co-promotion fees	3,309	4,915
Accrued other	1,869	717
Total accrued liabilities	$ 7,851	$ 7,594

Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Recurring \| Level I \| Money market funds
Fair value measurements
Financial Assets	$ 33.2	$ 70.0

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2013
Preferred stock liability
Changes in the fair value of the Company's Level 3 financial liabilities
Settlement of preferred stock	$ (2,700)
Recurring \| Level 3
Changes in the fair value of the Company's Level 3 financial liabilities
Beginning balance		$ 583
Recurring \| Level 3 \| Preferred stock liability
Changes in the fair value of the Company's Level 3 financial liabilities
Change in fair value of preferred stock liability recorded as other expense, net		2,070
Settlement of preferred stock		(2,653)
Recurring \| Level 3 \| Preferred stock warrant liability
Changes in the fair value of the Company's Level 3 financial liabilities
Fair value of liability		175
Change in fair value of preferred stock liability recorded as other expense, net		86
Conversion of preferred stock warrant liability		$ (261)

Fair Value Measurements (Details 3) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jun. 17, 2013	Nov. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Nov. 03, 2013	Jun. 30, 2013
Fair value measurements
Change in value of preferred stock liability			$ 2,070	$ (278)
Series C
Assumptions used to calculate fair value of preferred stock liability using the option-pricing method
Estimated fair value common stock (in dollars per share)	$ 2.39	$ 1.78			$ 13.14	$ 2.40
Preferred stock liability
Fair value measurements
Fair value of liability	$ 2,700	$ 900		600
Change in value of preferred stock liability	$ 2,100			$ (300)
Assumptions used to calculate fair value of preferred stock liability using the option-pricing method
Probability of success of the second tranche (as a percent)	100.00%	100.00%
Term	1 day	8 months 1 day
Expected volatility (as a percent)	36.40%	44.00%

Commitments and Contingencies (Details)	12 Months Ended
Commitments and Contingencies (Details)	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Operating Leases
Restricted cash	$ 118,000	$ 118,000
Future minimum lease payments under non-cancelable operating leases
2015	989,000
2016	413,000
2017	222,000
2018	130,000
Total minimum lease payments	1,754,000
Facilities rent expense	$ 852,000	840,000	$ 711,000
Supplies Purchase Commitments
Number of suppliers with which Company has non-cancelable purchase commitment \| item	2
Non-cancelable purchase commitment	$ 715,000
Laboratory facilities, Austin, Texas
Operating Leases
Cash security deposit	$ 75,000	$ 75,000

Debt (Details)	1 Months Ended		12 Months Ended
Debt (Details)	Dec. 31, 2014 USD ($) tranche installment	Jun. 30, 2013 USD ($) installment $ / shares shares	Dec. 31, 2014 USD ($) tranche installment	Dec. 31, 2013 USD ($)	Dec. 01, 2014 USD ($)	Nov. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Nov. 30, 2013 $ / shares	Nov. 03, 2013 USD ($)
Debt
Amount drawn down		$ 5,000,000
Cash paid for interest on debt			$ 307,000	$ 132,000
Long-term debt, net of current portion	$ 4,923,000		4,923,000	4,899,000
Interest expense on debt
Total			81,000	42,000
Convertible Preferred Stock Warrants
Interest expense on debt
Exercise price of warrant to purchase shares of Series C convertible preferred stock (in dollars per share) \| $ / shares		$ 7.56						$ 7.56
Number of shares for which warrant became exercisable \| shares		24,801
Aggregate fair value of the warrant for the shares exercisable under the warrant		$ 175,000							$ 261,000
Amortization period of debt discount		48 months
Term Loans
Debt
Maximum borrowing capacity	$ 15,000,000	$ 10,000,000	$ 15,000,000
Amount not drawn							$ 5,000,000
Number of installments \| installment	24		24
Period after which debt is repayable	24 months
Prepayment penalties for prepayment within one year of the loan origination (as a percent)	2.00%
Prepayment penalties for prepayment within two years of the loan origination (as a percent)	1.00%
Prepayment penalties for prepayment after two years of the loan origination (as a percent)	0.00%
Number of tranches \| tranche	3		3
Cash paid for interest on debt	$ 14,000
End-of term payment	110,000
Amount of prepayment premium waived						$ 75,000
Amount of end of term payment	237,500		$ 237,500		$ 110,000	$ 225,000
Third-party fees paid	45,000
Debt and unpaid accrued end-of-term payment	5,003,000		5,003,000	5,042,000
Unamortized note discount	(80,000)		(80,000)	(143,000)
Net debt obligation	4,923,000		4,923,000	4,899,000
Future principal payments
2017	2,437,000		2,437,000
2018	2,563,000		2,563,000
Total	$ 5,000,000		5,000,000
Interest expense on debt
End of term payment as a percentage of total outstanding principal balance	4.75%
Nominal interest			296,000	158,000
Amortization of debt discount			62,000	33,000
End of term payment interest			81,000	42,000
Total			439,000	$ 233,000
Term Loans \| Term Loan Due 2017
Debt
Amount drawn down		$ 5,000,000
Number of installments \| installment		30
Period after which debt is repayable		18 months
Interest rate (as a percent)		6.06%
Prepayment penalties for prepayment within one year of the loan origination (as a percent)		2.25%
Prepayment penalties for prepayment within two years of the loan origination (as a percent)		1.50%
Prepayment penalties for prepayment after two years of the loan origination (as a percent)		0.75%
Repayment of debt	$ 5,000,000
Term Loans \| Term Loan Tranche One
Debt
Maximum borrowing capacity	5,000,000		$ 5,000,000
Amount drawn down	$ 5,000,000
Interest rate (as a percent)	5.00%		5.00%
Term Loans \| Term Loan Tranche Two
Debt
Maximum borrowing capacity	$ 5,000,000		$ 5,000,000
Amount drawn down	5,000,000
Term Loans \| Term Loan Tranche Three
Debt
Maximum borrowing capacity	$ 5,000,000		$ 5,000,000

Convertible Preferred Stock Warrant (Details) - USD ($)		1 Months Ended		12 Months Ended
Convertible Preferred Stock Warrant (Details) - USD ($)	Nov. 03, 2013	Mar. 31, 2014	Jun. 30, 2013	Dec. 31, 2013	Nov. 30, 2013	Jun. 17, 2013	Nov. 30, 2012
Convertible preferred stock warrant
Amount drawn down on term loan			$ 5,000,000
Assumptions used to calculate fair value of warrant upon issuance using Black-Scholes option-pricing valuation model
Amount of change in the fair value reported as an expense in other income (expense), net				$ 86,000
Series C
Assumptions used to calculate fair value of warrant upon issuance using Black-Scholes option-pricing valuation model
Estimated fair value common stock (in dollars per share)	$ 13.14		$ 2.40			$ 2.39	$ 1.78
Convertible Preferred Stock Warrants
Convertible preferred stock warrant
Number of shares of preferred stock that can be purchased by each warrant			49,602
Exercise price of warrant to purchase shares of Series C convertible preferred stock (in dollars per share)			$ 7.56		$ 7.56
Number of shares for which warrant became exercisable			24,801		24,801
Number of warrants exercised		24,801
Issuance of common stock on cashless exercise of warrant (in shares)		13,739
Fair value of currently exercisable portion of the warrant	$ 261,000		$ 175,000
Assumptions used to calculate fair value of warrant upon issuance using Black-Scholes option-pricing valuation model
Contractual term	7 years		7 years 3 months 18 days
Risk-free interest rate (as a percent)	2.00%		2.10%
Expected volatility (as a percent)	81.40%		73.70%
Expected dividend yield (as a percent)	0.00%		0.00%
Amount of change in the fair value reported as an expense in other income (expense), net				$ 86,000

Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Nov. 04, 2013	Jun. 17, 2013	Jun. 30, 2013	Nov. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Nov. 03, 2013
Convertible preferred stock
Preferred stock liability valuation decrease recorded in other income (expense), net					$ (2,070)	$ 278
Preferred stock liability
Assumptions used to calculate fair value of preferred stock liability using the option-pricing method
Probability of success of the second tranche (as a percent)		100.00%		100.00%
Contractual term		1 day		8 months 1 day
Expected volatility (as a percent)		36.40%		44.00%
Convertible preferred stock
Preferred stock liability		$ 2,700		$ 900		600
Preferred stock liability valuation decrease recorded in other income (expense), net		$ (2,100)				$ 300
Preferred stock liability settled			$ (2,700)
Common Stock
Assumptions used to calculate fair value of preferred stock liability using the option-pricing method
Estimated fair value common stock (in dollars per share)	$ 13.00				$ 14.50		$ 9.66
Convertible preferred stock
Conversion of preferred stock into common stock upon initial public offering (in shares)	14,997,312				14,997,312
Convertible Preferred Stock.
Convertible preferred stock
Convertible preferred stock converted to common stock (in shares)	59,989,268
Conversion of preferred stock into common stock upon initial public offering (in shares)					(59,989,268)
Series C
Assumptions used to calculate fair value of preferred stock liability using the option-pricing method
Estimated fair value common stock (in dollars per share)		$ 2.39	$ 2.40	$ 1.78				$ 13.14

Stockholders' Equity (Details)	12 Months Ended
Stockholders' Equity (Details)	Dec. 31, 2014 USD ($) Vote $ / shares shares	Dec. 31, 2013 $ / shares shares	Nov. 04, 2013 $ / shares shares	Dec. 31, 2012 shares	Dec. 31, 2011 shares
Stockholders' Equity
Authorized shares of common stock	125,000,000	125,000,000
Par value of shares of common stock (in dollars per share) \| $ / shares	$ 0.001	$ 0.001
Number of votes for each share of stock \| Vote	1
Dividends declared \| $	$ 0
Common Stock
Options issued and outstanding (in shares)	3,249,469	2,359,287		2,227,669	1,429,737
Options available for grant under stock option plans (in shares)	1,341,252	1,787,802		347,386	474,961
Shares of common stock reserved for issuance	4,590,721	4,171,890
Preferred stock, shares authorized	5,000,000	5,000,000	5,000,000
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.001	$ 0.001	$ 0.001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Options
Common Stock
Options issued and outstanding (in shares)	3,249,469	2,359,287
Options available for grant under stock option plans (in shares)	1,341,252	1,787,802
Common Stock Warrants
Common Stock
Common stock warrants issued and outstanding (in shares)		24,801

Stock Incentive Plans (Details) - shares		12 Months Ended
Stock Incentive Plans (Details) - shares	Feb. 15, 2008	Dec. 31, 2014	Dec. 31, 2013	Oct. 02, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock incentive plans
Number of shares available for issuance		1,341,252	1,787,802		347,386	474,961
Options
Stock incentive plans
Number of shares available for issuance		1,341,252	1,787,802
2008 Plan \| Options \| Minimum
Stock incentive plans
Exercise price of options granted expressed as a percentage of its fair value	100.00%
2008 Plan \| Options \| Maximum
Stock incentive plans
Term of options granted	10 years
2008 Plan \| Options \| Newly hired employee
Stock incentive plans
Vesting period	4 years
Percentage of award vesting after one year	25.00%
2008 Plan \| ISO \| Minimum
Stock incentive plans
Voting power of person owning stock (as a percent)	10.00%
Option price as a percentage of estimated fair value of shares on date of grant to a person owning stock representing more than 10% of voting power of all classes of stock	110.00%
2008 Plan \| ISO \| Maximum
Stock incentive plans
Term of options granted to a person owning stock representing more than 10% of voting power of all classes of stock	5 years
2013 Plan
Stock incentive plans
Number of additional shares reserved for issuance				1,700,000
Maximum annual increase in outstanding shares on the last day of the immediately preceding fiscal year (as a percent)		4.00%
Number of shares available for issuance		1,341,252
2013 Plan \| Options \| Outside director serving as a member of Board of Directors for at least six months
Stock incentive plans
Shares granted as annual grant		10,000
2013 Plan \| Options \| Outside director serving as a member of Board of Directors for at least six months \| Minimum
Stock incentive plans
Period for which director has to serve as board of director to receive grant to purchase shares		6 months
2013 Plan \| Options \| Outside director
Stock incentive plans
Exercise price of options granted expressed as a percentage of its fair value		100.00%
2013 Plan \| Options \| Outside director \| Maximum
Stock incentive plans
Expiration period after termination of service		12 months
2013 Plan \| ISO \| Minimum
Stock incentive plans
Exercise price of options granted expressed as a percentage of its fair value		100.00%
2013 Plan \| ISO \| Maximum
Stock incentive plans
Term of options granted		10 years
2013 Plan \| NSO \| Minimum
Stock incentive plans
Exercise price of options granted expressed as a percentage of its fair value		100.00%
2013 Plan \| NSO \| Outside director who was not previously an employee
Stock incentive plans
Percentage of award vesting after one year		25.00%
Shares granted as initial grant		35,000
Percentage of award granted which vests on a monthly basis		0.75
Period over which remaining shares will vest on a monthly basis		3 years

Stock Incentive Plans (Details 2) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 04, 2013
Shares Available for Grant
Balance at the beginning of the period (in shares)	1,787,802	347,386	474,961
Additional options authorized (in shares)	845,732	1,950,000	743,100
Granted (in shares)	(1,488,492)	(695,029)	(931,944)
Canceled (in shares)	196,210	185,445	61,269
Balance at the end of the period (in shares)	1,341,252	1,787,802	347,386	474,961
Stock Options Outstanding
Balance at beginning of the period (in shares)	2,359,287	2,227,669	1,429,737
Granted (in shares)	1,488,492	695,029	931,944
Canceled (in shares)	(196,210)	(185,445)	(61,269)
Exercised (in shares)	(402,100)	(377,966)	(72,743)
Balance at the end of the period (in shares)	3,249,469	2,359,287	2,227,669	1,429,737
Options vested and exercisable at the end of the period (in shares)	1,370,944
Options vested and expected to vest at the end of the period (in shares)	3,092,476
Weighted Average Exercise Price
Balance at beginning of the period (in dollars per share)	$ 3.07	$ 2.06	$ 1.55
Granted (in dollars per share)	13.38	5.32	2.78
Canceled (in dollars per share)	9.37	2.69	1.97
Exercised (in dollars per share)	1.68	1.46	1.05
Balance at the end of the period (in dollars per share)	7.59	$ 3.07	$ 2.06	$ 1.55
Options vested and exercisable at the end of the period (in dollars per share)	2.92
Options vested and expected to vest at the end of the period (in dollars per share)	$ 7.32
Weighted Average Remaining Contractual Life
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	7 years 10 months 17 days	7 years 10 months 2 days	8 years 2 months 1 day	8 years 2 months 19 days
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	7 years 10 months 17 days	7 years 10 months 2 days	8 years 2 months 1 day	8 years 2 months 19 days
Options vested and exercisable at the end of the period	6 years 5 months 9 days
Options vested and expected to vest at the end of the period	7 years 9 months 22 days
Aggregate Intrinsic Value
Balance at the beginning of the period (in dollars)	$ 26,964	$ 4,311	$ 1,221
Balance at the end of the period (in dollars)	12,400	$ 26,964	$ 4,311	$ 1,221
Options vested and exercisable at the end of the period (in dollars)	9,287
Options vested and expected to vest at the end of the period (in dollars)	$ 12,295
Common Stock
Stock Options Outstanding
Exercised (in shares)	(402,100)	(377,966)	(72,743)
Additional disclosures
Estimated fair value common stock (in dollars per share)	$ 9.66	$ 14.50			$ 13.00

Stock Incentive Plans (Details 3) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Incentive Plans
Weighted average fair value of options to purchase common stock granted (in dollars per share)	$ 9.08	$ 4.19	$ 1.95
Weighted average fair value of vested options (in dollars per share)	3.07	2.12	$ 1.40
Stock incentive plans
Weighted average fair value of stock options exercised (in dollars per share)	$ 1.18	$ 0.97
Intrinsic value of stock options exercised (in dollars)	$ 3.2	$ 4.9	$ 0.2
Employee stock options
Stock incentive plans
Total estimated grant date fair value of options to purchase common stock vested (in dollars)	$ 1.6	$ 1.3

Stock Incentive Plans (Details 4) - USD ($) $ in Thousands	12 Months Ended
Stock Incentive Plans (Details 4) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based Compensation
Stock-based compensation
Share-based compensation expense (in dollars)	$ 3,548	$ 1,247	$ 675
Unrecognized compensation expense (in dollars)	$ 9,900
Period over which unrecognized compensation expense expected to be recognized	3 years
Stock-based Compensation \| Cost of revenue
Stock-based compensation
Share-based compensation expense (in dollars)	$ 51	34	26
Stock-based Compensation \| Research and development
Stock-based compensation
Share-based compensation expense (in dollars)	790	250	131
Stock-based Compensation \| Selling and marketing
Stock-based compensation
Share-based compensation expense (in dollars)	707	169	111
Stock-based Compensation \| General and administrative
Stock-based compensation
Share-based compensation expense (in dollars)	$ 2,000	$ 794	$ 407
Stock-based Compensation, employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average volatility, low end of range (as a percent)	70.19%	80.42%	82.07%
Weighted-average volatility, high end of range (as a percent)	78.54%	81.41%	84.33%
Risk-free interest rate, low end of range (as a percent)	1.66%	0.88%	0.65%
Risk-free interest rate, high end of range (as a percent)	2.04%	2.11%	1.19%
Stock-based Compensation, employees \| Minimum
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term	5 years 6 months	5 years	5 years
Stock-based Compensation, employees \| Maximum
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term	6 years 29 days	6 years 29 days	6 years 29 days
Stock-based Compensation, non-employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average volatility, low end of range (as a percent)	73.20%	77.86%	81.14%
Weighted-average volatility, high end of range (as a percent)	74.48%	78.14%	82.11%
Risk-free interest rate, low end of range (as a percent)	2.09%	2.59%	1.43%
Risk-free interest rate, high end of range (as a percent)	2.20%	2.99%	1.77%
Stock-based Compensation, non-employees \| Minimum
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term	8 years 9 months	7 years 8 months 19 days	8 years 2 months 23 days
Stock-based Compensation, non-employees \| Maximum
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term	10 years	9 years 9 months	9 years 11 months 5 days

Stock Incentive Plans (Details 5) - USD ($)	1 Months Ended	12 Months Ended
Stock Incentive Plans (Details 5) - USD ($)	Feb. 28, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based compensation
Options granted (in shares)		1,488,492	695,029	931,944
Weighted average fair value of stock options vested (in dollars per share)		$ 3.07	$ 2.12	$ 1.40
Equity-based Compensation, executive bonuses
Stock-based compensation
Options granted (in shares)	100,498
Weighted average fair value of stock options vested (in dollars per share)	$ 2.59
Share-based compensation expense (in dollars)				$ 259,000

Genzyme Co-promotion Agreement (Details)			1 Months Ended	2 Months Ended	7 Months Ended	10 Months Ended	12 Months Ended			14 Months Ended
Genzyme Co-promotion Agreement (Details)	Jan. 01, 2015	Aug. 12, 2014	Feb. 29, 2012 USD ($)	Jan. 31, 2015	Aug. 11, 2014	Dec. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Feb. 27, 2014	Feb. 13, 2015 country	Nov. 07, 2014 country	Jan. 31, 2012 country
Genzyme Co-promotion Agreement
Co-promotion fee received from Genzyme									$ 10,000,000
Amortization of up-front co-promotion fee							$ 2,269,000	$ 2,500,000	2,386,000
Co-promotion agreement \| Genzyme
Genzyme Co-promotion Agreement
Co-promotion expenses							12,000,000	8,600,000	5,500,000
Outstanding obligation to Genzyme						$ 6,000,000	6,000,000	6,700,000
Amortization of up-front co-promotion fee							2,300,000	2,500,000	$ 2,400,000
Co-promotion agreement \| Genzyme \| Accounts payable
Genzyme Co-promotion Agreement
Outstanding obligation to Genzyme						2,700,000	2,700,000	1,800,000
Co-promotion agreement \| Genzyme \| Accrued liabilities
Genzyme Co-promotion Agreement
Outstanding obligation to Genzyme						$ 3,300,000	3,300,000	$ 4,900,000
Afirma thyroid diagnostic solution co-promotion agreement \| Genzyme
Genzyme Co-promotion Agreement
Number of countries outside United States for exclusive promotion under the agreement \| country													40
Co-promotion fee received from Genzyme			$ 10,000,000
Co-promotion fees as a percentage of cash receipts						32.00%			50.00%	40.00%
Maximum amount to be spent by co-promoter for qualifying clinical development activities in countries that require additional testing							$ 500,000
Co-promotion fees as a percentage of cash receipts for remaining periods	15.00%
Amortization period of co-promotion fee					4 years
Termination notification period		6 months
Ex-U.S. Co-Promotion Agreement \| Genzyme
Genzyme Co-promotion Agreement
Number of countries outside United States for exclusive promotion under the agreement \| country												6
Co-promotion fees as a percentage of cash receipts				32.00%
Ex-U.S. Co-Promotion Agreement \| Genzyme \| Subsequent Event
Genzyme Co-promotion Agreement
Number of countries outside United States for exclusive promotion under the agreement \| country											5

- Details

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Thyroid Cytopathology Partners (Details) - USD ($)	12 Months Ended
Thyroid Cytopathology Partners (Details) - USD ($)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Thyroid Cytopathology Partners
Outstanding obligations	$ 7,397,000	$ 5,294,000
Thyroid Cytopathology Partners
Thyroid Cytopathology Partners
Notice of intent not to renew period	12 months
Expenses for cytopathology testing and evaluation services	$ 4,000,000	3,200,000	$ 1,800,000
Outstanding obligations	1,100,000	600,000
Reduction to rent expense for TCP's portion of costs for shared space	$ 86,000	49,000
Reimbursed rent		59,000
Excess payment included in accounts payable		$ 10,000

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes
Pretax loss	$ 29,400	$ 25,600	$ 18,600
Reconciliation of tax expense computed at the statutory federal rate and the Company's tax expense
U.S. federal taxes at statutory rate	(9,987)	(8,697)	(6,341)
State taxes (net of federal benefit)	5	11	(1,074)
Permanent differences	64	790	(23)
Incentive stock options	672	355	284
Tax credits	(461)	(502)	(113)
Change in valuation allowance	9,707	8,043	7,267
Current deferred tax assets:
Genzyme co-promotion agreement	793	1,005	1,001
Accruals and deferred rent	1,819	599	148
Gross deferred tax assets	2,612	1,604	1,149
Valuation allowance	(2,312)	(1,603)	(1,145)
Net deferred tax assets	300	1	4
Non-current deferred tax assets:
Net operating loss carryforwards	41,971	28,569	20,536
Research and development credits	1,916	1,455	954
Stock-based compensation	826	313	154
Genzyme co-promotion agreement	202	787	2,048
Accruals, deferred rent and other	1,562	106	9
Gross deferred tax assets	46,477	31,230	23,701
Valuation allowance	(41,127)	(31,216)	(23,622)
Net deferred tax assets	5,350	14	79
Deferred tax liabilities:
Property and equipment	(60)	(15)	(83)
In-process research and development	(5,590)
Gross deferred tax liabilities	(5,650)	(15)	(83)
Net non-current deferred tax liabilities	(300)	(1)	$ (4)
Increase in valuation allowance against deferred tax assets	10,600	$ 8,100
Operating loss carryforwards
Federal and state net operating loss carryforwards related to stock-based compensation	200
Federal
Operating loss carryforwards
Net operating loss carryforwards	113,600
State
Operating loss carryforwards
Net operating loss carryforwards	$ 60,600

Income Taxes (Details 2) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Unrecognized tax benefits, beginning of period	$ 727	$ 481	$ 341
Gross increases-tax position in prior period	548	68	67
Gross increases-current period tax positions	296	178	73
Unrecognized tax benefits, end of period	1,571	$ 727	$ 481
Interest expense or penalties related to unrecognized tax benefits	0
Federal
Credit carryforwards
Credit carryforwards available to reduce future taxable income	2,200
State
Credit carryforwards
Credit carryforwards available to reduce future taxable income	$ 1,600

Income Taxes (Details 3)	12 Months Ended
Income Taxes (Details 3)	Dec. 31, 2014
Federal
Income tax examination
Income tax examination period	3 years
State
Income tax examination
Income tax examination period	4 years

401(k) Plan (Details) - USD ($)	12 Months Ended
401(k) Plan (Details) - USD ($)	Dec. 31, 2014	Dec. 31, 2013
401(k) Plan
Employer contributions to the plan	$ 0	$ 0

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected Quarterly Financial Data (Unaudited)
Total revenues	$ 12,199	$ 9,838	$ 8,677	$ 7,476	$ 6,838	$ 5,594	$ 5,068	$ 4,384	$ 38,190	$ 21,884	$ 11,628
Net loss	$ (8,142)	$ (7,902)	$ (6,655)	$ (6,674)	$ (5,892)	$ (6,303)	$ (6,490)	$ (6,895)	$ (29,373)	$ (25,580)	$ (18,649)
Net loss per common share, basic and diluted	$ (0.36)	$ (0.37)	$ (0.31)	$ (0.32)	$ (0.42)	$ (6.59)	$ (7.53)	$ (9.04)	$ (1.36)	$ (6.15)	$ (28.68)
Shares used to compute net loss per common share, basic and diluted (in shares)	22,508,250	21,648,660	21,237,196	21,148,342	13,944,239	955,890	861,839	763,021	21,639,374	4,158,664	650,333

Subsequent Event (Unaudited) (Details) - Ex-U.S. Co-Promotion Agreement - Genzyme - country	Jan. 01, 2015	Feb. 13, 2015	Nov. 07, 2014
Subsequent Events
Number of countries outside United States for exclusive promotion under the agreement			6
Subsequent Event
Subsequent Events
Number of countries outside United States for exclusive promotion under the agreement		5
Co-promotion fee paid as a percentage of net revenue	25.00%
Period of agreement	5 years