Balance Sheet Components - Components of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Payables And Accruals [Abstract] | ||
| Clinical studies | $ 1,375 | $ 756 |
| Accrued interest payable on debt | 862 | 0 |
| Professional fees | 620 | 880 |
| Debt financing fees | 600 | 0 |
| Test sample processing fees | 524 | 426 |
| Accrued overpayments and refunds | 281 | 163 |
| Software implementation costs | 176 | 0 |
| Deferred rent – current portion | 374 | 258 |
| Capital leases – current portion | 68 | 71 |
| Other accrued expenses | 440 | 338 |
| Total accrued and other liabilities | $ 5,320 | $ 2,892 |