Comparison of various D-dimer tests for the diagnosis of deep venous thrombosis.

Analyses of D-dimers in plasma are frequently used as diagnostic tools for deep venous thrombosis (DVT). Enzyme-linked immunosorbent assays (ELISAs) are considered to be the method of choice for quantitative assays, but are time consuming. Therefore, we have assessed plasma levels of D-dimers in patients with clinically suspected DVT using quantitative (Asserachrom D-Di ELISA and TintElize), semiquantitative (Minutex latex, D-Di latex, NycoCard D-Dimer) and qualitative (INSTANT.I.A) assays. Phlebography was used as the gold standard to verify or exclude the suspected diagnosis. We conclude that the fast assays, INSTANT.I.A and Minutex, have essentially the same negative predictive value [91% and 89%, respectively, using a cut-off value < 0.5 mg/l fibrinogen equivalent units (FEU)] for excluding DVT as the Asserachrom D-Di ELISA and TintElize tests (92%). The D-Di Latex assay had a negative predictive value of 82% (cut-off < 0.5 mg/l FEU) and turned out to be less useful in our material. The NycoCard D-dimer assay had a negative predictive value of 100% when using the cut-off value < 0.5 mg/l FEU, but this was substantially lower when the cut-off was changed to < or = 0.5 mg/l. Thus, we conclude that several fast tests offer a simpler and more rapid way of determining plasma levels of D-dimer than conventional ELISA methods without loss of clinical usefulness in excluding DVT.