ASSESSMENT OF MATERIAL-INDUCED PROCOAGULANT ACTIVITY BY A MODIFIED RUSSELL VIPER VENOM COAGULATION TIME TEST

Platelet activation is an inevitable consequence of blood-material int eractions. The ability of those activated platelets and platelet-deriv ed microparticles to enhance coagulation reactions leading to thrombin /fibrin formation has not been well studied despite its potential sign ificance. Activated platelets and platelet-derived microparticles are known to dramatically enhance the catalytic efficiencies of the tenase and prothrombinase complexes. In this paper, a modified Russell viper venom coagulation time test is used to quantitate material-induced pr ocoagulant activity due to the generation of activated phospholipid su rfaces. In our test system, polyethylene and Silastic(TM) tubes were f illed with heparinized whole blood and left to gently flow back and fo rth at 37 degrees C. After 1 h, the blood within the tubes was gravity drained and the plasma fraction assayed for procoagulant activity. Th e clotting times were determined by a Coag-A-Mate X2 instrument after the automated addition of Russell viper venom (to activate factors V a nd X) and calcium ions. Appreciable procoagulant activity was generate d during whole blood contact within polyethylene and Silastic(TM) tube s although significantly greater activity was generated by the latter surface. As previously reported, platelet-derived microparticles also were detected by flow cytometry. Filtration of the plasma after materi al contact through a 0.1 mu m filter led to substantial gains in clott ing times and to near complete removal of microparticles, indicating t hat the material-induced microparticles likely were responsible for th e procoagulant activity. (C) 1998 John Wiley & Sons, Inc.