Measuring thrombin generation based sensitivity to activated protein C using an automated coagulometer (ACL 9000)

Abstract

Increased thrombin generation in the presence of activated protein C (APC) is known to be an independent risk factor for thrombosis. Although commercially available methods for measuring thrombin generation are available, none measure sensitivity to APC. We have developed an automated thrombin generation based APC sensitivity test, for use with defibrinated plasma using the automated coagulometer (ACL9000). A chromogenic substrate that is cleaved by thrombin at a slow rate, 7 pm tissue factor and 20 μm phospholipid (DOPC : DOPE : DOPS, 60 : 20 : 20) with and without 5 nm APC. Thrombin generation with [endogenous thrombin potential (ETP)+APC] and without APC (ETP), was expressed as a ratio relative to pooled normal plasma. Normal reference ranges were established in 30 normal subjects: ETP 0.73-1.06; ETP+APC 0.42-1.07. ETP+APC was found to be sensitive to factor V Leiden, oral contraceptive use, low levels of protein S and tissue factor pathway inhibitor and increased plasma factor VIII. © 2007 Blackwell Publishing Ltd.