Effect of Specimen Collection on Routine Coagulation Assays and D-Dimer Measurement

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Abstract
Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, and D-dimer assays are part of the conventional routine coagulation panel. Accurate standardization of both the preanalytical and analytical phases is pivotal to achieving accuracy and precision of results. Routine blood coagulation assays and D-dimer testing strongly influence clinical decision-making because they represent crucial steps in the diagnostic approach to thromboembolic and hemorrhagic disorders and in the monitoring of anticoagulant therapy with heparin or oral anticoagulants. Among major determinants of preanalytical variability, sample collection exerts considerable influence on the reliability of results (1); problems arising from cumbersome blood withdrawal, inadequate filling or mixing of the tube, and inappropriate treatment of specimens are important sources of imprecision. In particular, it has been suggested that the precision of fibrinogen measurements might be influenced by procedures used for specimen collection, leading to the suggestion that the first tube of blood collected be discarded (2). To establish the potential impact of sample collection on imprecision of routine coagulation assays, we measured PT, aPTT, fibrinogen, and D-dimer in 30 consecutive patients on oral anticoagulant therapy. The study was …