Assessment of fibrinolytic activity by measuring the lysis time of a tissue-factor-induced clot: a feasibility evaluation.

A clot lysis time assay in which a tissue factor-induced fibrin clot is lysed by exogenously added tissue plasminogen activator has been recently reported. We evaluated the feasibility of clot lysis time in a routine hemostasis laboratory, and its correlation with thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 levels and changes with aging in 185 healthy participants. Clot lysis time was assessed by monitoring changes in turbidity during clot formation and subsequent lysis using a computerized kinetic spectrophotometric microtiter plate. After preliminary experiments, 100 and 160 ng/mL tissue plasminogen activator concentrations were chosen for the study. Clot lysis time was calculated by a new mathematical analysis of the lysis curve based on discrete derivative. Clot lysis time, thrombin activatable fibrinolysis inhibitor, and plasminogen activator inhibitor-1 plasma levels showed a normal distribution. For both concentrations of tissue plasminogen activator, clot lysis time progressively increased with increase in age (P < .0001) and was significantly correlated with thrombin activatable fibrinolysis inhibitor antigen, thrombin activatable fibrinolysis inhibitor activity, and plasminogen activator inhibitor-1 antigen (at least P < .01). During linear regression analysis, thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 antigen were found to significantly influence clot lysis time (at least P < .01). Clot lysis time determination has a good laboratory performance. Our new method of calculation is independent of the time of reading and allows a more accurate and consistent detection of both short and prolonged lysis times. Our data suggest the feasibility of the use of this test in the work of routine hemostasis laboratory.