Clinical evaluation of eight different D-dimer tests for the exclusion of deep venous thrombosis in primary care patients.

D-dimer tests are an essential element in the diagnostic work-up of deep venous thrombosis (DVT). However, the poor standardization amongst assays necessitates clinical validation before implementation in daily practice. We therefore evaluated the analytical and diagnostic performance of eight D-dimer tests in a representative group of 290 prospectively identified consecutive primary care patients with suspected DVT. Seven quantitative D-dimer assays, and a qualitative test, Simplify, were evaluated. Correlation between assays was generally poor and several assays showed a significant bias in the method comparison. Nevertheless, the Vidas D-dimer, Innovance D-dimer (CA1500 and BCS), Pathfast D-dimer, and HemosIL HS500 (ACL TOP), all displayed 100% (95% CI: 85-100%) sensitivity. Tina-quant (Modular), AQT90 D-dimer, and Liatest (STA(®)) D-dimer tests showed a slightly lower sensitivity of 95% (78-100%). and the Simplify test reached a sensitivity of 91% (72-99%) that was further improved in combination with a clinical decision rule to 95% (76-100%). In concert with the low (8.2%) prevalence of proximal DVT, diagnosed by compression ultrasonography, in our study, all test reached a negative predictive value (NPV) of at least 99%. The user friendliness of the assays differed mainly by stability of reagents, calibration frequency, time required to obtain a test result and costs of a test. In conclusion, despite considerable analytical differences, in our low-risk population all tests evaluated displayed an excellent NPV. In combination with a validated clinical decision rule to identify low-risk patients, even a straightforward POC solution could safely and cost-efficiently rule out DVT.