Exclusion of deep venous thrombosis with D-dimer testing--comparison of 13 D-dimer methods in 99 outpatients suspected of deep venous thrombosis using venography as reference standard.

In a direct assay comparison we evaluated the diagnostic performance of 10 novel D-Dimer assays for the exclusion of deep venous thrombosis (DVT). In addition, 3 conventional ELISA D-Dimer assays were included as reference tests. The study was performed in 99 consecutive outpatients referred to the emergency department for clinical suspicion of DVT. Venography was used as reference standard and demonstrated the presence of DVT in 50 patients (6 patients with isolated distal DVT and 44 patients with proximal DVT). The qualitative D-Dimer assays Minutex and SimpliRED and the quantitative BC DD showed overall sensitivities (for proximal and distal DVT) of only 80-83% with specificities that ranged from 87 to 94%. Overall sensitivity was 94% for the qualitative INSTANT I.A. and 98% for the quantitative Turbiquant at a cut-off level equal to the detection limit. Using different cut-off levels a sensitivity of 100% for proximal DVT and for proximal as well as distal DVT could be obtained for NycoCard, IL DD, Liatest, Tinaquant and VIDAS D-Dimer assays with specificities that ranged from 31% (NycoCard) to 71% (VIDAS) for proximal DVT and from 12% (NycoCard) to 47% (IL DD) for overall DVT. At a cut-off level equal to the upper limit of the reference range only Tinaquant and VIDAS showed a sensitivity of 100% for proximal as well as for distal DVT with a specificity of 39% and 41% respectively. The results of this study suggest that the VIDAS and Tinaquant D-Dimer assays have the highest sensitivity for the exclusion of DVT in outpatients. In outpatients that have a low or moderate pretest probability for DVT, these tests may be used in management studies where anticoagulation is withheld on the basis of D-Dimer testing alone.

One-step chromogenic equivalent of activated partial thromboplastin time evaluated for clinical application.

We evaluated the clinical usefulness of a recently developed semi-automated one-step chromogenic equivalent of activated partial thromboplastin time (APTT; Behring). This simple test is easily adaptable for automation. Generally, the results with this chromogenic one-step APTT were at least as precise as those obtained with comparative coagulometric methods. The chromogenic one-step APTT showed, both in vitro and in vivo, adequate sensitivity to congenital intrinsic factor deficiency but no sensitivity to Factor VII deficiency. Unlike a two-step coagulometric APTT (Dade), the one-step chromogenic APTT seemed sensitive to activation products of the contact system, which are present in immunoadsorbed factor-deficient plasma. The in vitro sensitivity of the chromogenic APTT to heparin was comparable with that of a coagulometric APTT, but the sensitivity to heparin in patients' samples differed slightly. The chromogenic APTT is relatively insensitive to anomalies in the fibrinogen-fibrin conversion. Finally, we observed discrepancies between the chromogenic and coagulometric APTT results for plasma of patients with disseminated intravascular coagulation. We conclude that this one-step chromogenic APTT warrants further evaluation for possible use as a routine test for the clinical laboratory.