Clinical and Applied Thrombosis/Hemostasis

 

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Clinical and Applied Thrombosis/Hemostasis, Vol. 14, No. 3, 303-318 (2008)
DOI: 10.1177/1076029607309255

The Extrinsic Coagulation Activity Assay

Thomas W. Stief, MD

Department of Clinical Chemistry, Central Laboratory, University Hospital, Marburg, Germany, thstief{at}med.uni-marburg.de

Aleksandra Wieczerzak

Department of Clinical Chemistry, Central Laboratory, University Hospital, Marburg, Germany

Harald Renz, MD

Department of Clinical Chemistry, Central Laboratory, University Hospital, Marburg, Germany

A chromogenic assay for the tissue factor—mediated thrombin generation was developed, the extrinsic coagulation activity assay: 50 µL citrated plasma is incubated with 5 µL tissue factor in 6% albumin and 250 mM CaCl2. After 1-minute (37°C) coagulation reaction time, (extrinsic coagulation activity assay with 1-minute coagulation reaction time; generating normally about 1 IU/mL thrombin) 100 µL 2.5 M arginine is added to stop hemostasis activation. Generated thrombin is then chromogenically quantified. The normal extrinsic coagulation activity assay range is 100% ± 20%. Extrinsic coagulation activity assay in plasma of patients on heparin or coumarines is about 10-fold lower. Advantages of extrinsic coagulation activity assay: normal range of extrinsic hemostasis is truly represented, patients prone to hyper-activated extrinsic pathway are detected, anticoagulants result in respective test inhibition, fibrinogen/fibrin concentration does not artefactually alters the test result, plasma matrix is not changed significantly in the assay, and assay results are IU/mL thrombin or % of normal, which can be measured by every normal photometer.

Key Words: thrombin • EXCA • prothrombin time • hemostasis • laboratory medicine


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