Open AccessImproved Distinction of Factor V Wild-Type and Factor V Leiden Using a Novel Prothrombin-Based Activated Protein C Resistance Assay
Author(s) -
Marianne Wilmer,
Christoph Stöcker,
Beatrice Bühler,
Brigitte Conell,
Andreas Calatzis
Publication year - 2004
Publication title -
american journal of clinical pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.859
H-Index - 128
eISSN - 1943-7722
pISSN - 0002-9173
DOI - 10.1309/t8avvh7qwgl0qtf5
Subject(s) - factor v leiden , activated protein c resistance , factor v , protein c , microbiology and biotechnology , biology , medicine , thrombosis , venous thrombosis
A new prothrombin-based activated protein C resistance (APC-R) test is described. In this method, the patient sample is prediluted in a plasma depleted of factor V (FV). A reagent containing APC and a specific activator of FV is added. After an incubation period, clotting is initiated by the addition of the FV-dependent prothrombin activator Noscarin. We analyzed 703 samples from patients undergoing thrombophilia screening. By using a predefined cutoff ratio of 2.5, 100% sensitivity and specificity for the detection of a factor V Leiden (FVL) mutation was found. With a cutoff ratio of 1.2, a complete but narrow distinction of FVL heterozygous (n = 192) and FVL homozygous samples (n = 27) was determined. No interference by the international normalized ratio, activated partial thromboplastin time (aPTT), protein S activity, fibrinogen and factor VIII (FVIII) levels, or lupus anticoagulant ratio was detected. The new prothrombin-based APC-R assay provides improved distinction of FV wild-type and FVL carriers compared with the aPTT-based method. By the use of an FV-dependent prothrombin activator, the assay is not influenced by FVIII concentration or lupus anticoagulants.