The scientific basis for selection of measures of thrombogenicity.

The interaction of blood with materials is central in the thrombogenic response obtained in extracorporeal circulation. A number of processes are involved in determining whether there is generation of thrombin and the formation of an obstructive thrombus: these include activation of blood coagulation, platelet activation, trauma to the blood, blood flow, and use of anticoagulants (e.g. heparin). The way in which these processes produce their thrombogenic responses and interact is described to provide a basis for the understanding of the methodological approaches currently used to investigate thrombogenicity. It is concluded that much available methodology has limitations and no one indicator of the thrombogenic activity of a material or system (such as extracorporeal circulation) can be wholeheartedly recommended for all applications. Nevertheless, depending upon the circumstances of the particular investigation the assays to coagulation activation markers, thrombin-antithrombin III complex, prothrombin fragment F1+2 and fibrinopeptide A are emerging as valuable aids in the assessment of thrombogenicity. The information gained by use of these assays will require additional and complementary information from other assays of perhaps platelet function/activation, level of anticoagulant, and other coagulation markers.