COMPARISON OF THROMBIN-ANTITHROMBIN COMPLEX (TAT) LEVELS AND FIBRINOPEPTIDE-A FOLLOWING THROMBIN INCUBATION OF HUMAN PLASMA USING HIRUDIN AS AN INHIBITOR OF TAT FORMATION

Following incubation of citrated plasma with human thrombin, the interaction of thrombin with antithrombin III was measured as thrombin-antithrombin complex (TAT) concentration. Comparison was made to thrombin activity on fibrinogen, assayed as fibrinopeptide A (FPA). Light scattering studies were included to evaluate polymerization of fibrin. Hirudin, at a final concentration of 100 U/ml, effectively inhibited TAT generation at final thrombin concentrations below 0.4 NIH U/ml. Hirudin by itself did not affect the TAT ELISA analysis. TAT and FPA values correlated closely (r = 0.83, p < 0.001) and may equally well represent in vitro thrombin activity.