Point-of-Care D-Dimer Tests Exclude Deep Vein Thrombosis

Five point-of-care (POC) blood tests for fibrin degradation product D-dimer have been evaluated for their accuracy in diagnosing deep vein thrombosis (DVT).

D-dimer is a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis. POC D-dimer tests enable rapid exclusion of DVT without the need to refer a patient for conventional laboratory-based D-dimer testing.

Five D-dimer tests were evaluated at the University Medical Center Utrecht, (Utrecht, the Netherlands). The scientists analyzed data of 577 prospectively identified consecutive primary care patients suspected to have DVT. The patients underwent four quantitative D-dimer tests (Vidas, Pathfast, Cardiac, and Triage) and one qualitative test (Clearview Simplify). Ultrasonography was performed as the reference method. They evaluated the tests for the accuracy of their measurements and submitted a questionnaire to 20 users to assess the user-friendliness of each test.

The Vidas D-dimer test (bioMerieux; Marcy-l'Etoile, France), combines a two-step enzyme immunoassay sandwich method with fluorescent detection. The Pathfast D-dimer test (Mitsubishi Kagaku Iatron, Inc.; Tokyo, Japan), is a chemiluminescent enzyme immunoassay, which contains two D-dimer monoclonal antibodies, one labeled with alkaline phosphatase and the other coated with magnetic particles. The Cardiac D-dimer test (Roche Diagnostics, F. Hoffmann-La Roche Ltd., Basel, Switzerland), is based on a dual monoclonal antibody sandwich comprising a poly-streptadivin-biotin capture system with a gold particle label. The Triage D-dimer test (Biosite; San Diego CA, USA), uses single-marker fluorescence sandwich immunoassay uses the 3B6 D-Dimer antibody. The Clearview Simplify D-dimer test (Inverness Medical; Princeton, NJ, USA), is based on immunochromatography, and the test uses two D-dimer specific murine monoclonal antibodies, one of which is conjugated to colloidal gold particles.

All D-dimer tests showed negative predictive values higher than 98%. Sensitivity was high for all POC tests, with a range of 0.91 for Clearview Simplify to 0.99 for Vidas. Specificity varied between 0.39 for Pathfast and 0.64 for Clearview Simplify. The quantitative POC tests showed similar and high discriminative power for DVT. The quantitative Vidas and Pathfast devices showed limited user-friendliness for primary care, owing to a laborious calibration process and long analyzer warm-up time compared to the Cardiac and Triage. For the qualitative Clearview Simplify assay, no analyzer or calibration was needed, but interpretation of a test result was sometimes difficult because of poor color contrast. The study was published on September 15, 2010 in Clinical Chemistry.

Related Links:
University Medical Center Utrecht
bioMerieux
Mitsubishi Kagaku Iatron, Inc.
Roche Diagnostics
Biosite
Inverness Medical