Adaption of the plasmin generation assay to enhance sensitivity to plasminogen activator inhibitor-1 and establishment of sex-specific reference values in human plasma.

BACKGROUND

Pharmacologic modifiers of fibrinolysis are used to modulate bleeding and thrombosis. Characterization of a sensitive plasmin generation (PG) assay to identify abnormal fibrinolytic states and monitor antifibrinolytic medication may improve clinical care.

OBJECTIVES

To establish reference values of PG parameters, investigate sex-related differences, and study different regulators of fibrinolysis, using a PG assay.

METHODS

PG was assessed in plasma of 130 healthy individuals, normal pooled plasma, or factor-deficient plasma, using tissue factor or Russell viper venom-factor (F)X activator, with tissue plasminogen activator or the novel antifibrin urokinase plasminogen activator.

RESULTS

Reference values for PG parameters were established in plasma from healthy individuals. No PG was observed in plasminogen- or fibrinogen-deficient plasma. Thrombomodulin (TM), α2-antiplasmin, and tranexamic acid reduced PG. Inhibitory effects of TM in PG were counteracted using carboxypeptidase inhibitor, an inhibitor specific to active thrombin-activatable fibrinolysis inhibitor, confirming a role for thrombin-activatable fibrinolysis inhibitor and TM in modulating PG. Although the PG assay triggered with tissue plasminogen activator was insensitive to plasminogen activator inhibitor-1, it became sensitive to it when induced with antifibrin urokinase plasminogen activator. PG measurements in plasma of healthy individuals showed elevated PG levels in 11 of 13 female healthy donors taking oral contraceptives and an increased resistance to TM in females compared with that in males.

CONCLUSION

The PG assay is a specific and efficient tool to assess modulators of fibrinolysis and to study sex-related differences and has potential as a clinical tool to identify abnormal fibrinolytic profiles in patients and monitor antifibrinolytic drugs, such as tranexamic acid.