Hirudin for diagnostic purposes.

Hirudin serves as a versatile tool for the control of thrombin activity in hemostaseology. It may be added in excess to blood, plasma or test mixtures to prevent catalytic and nonenzymatic effects of thrombin. It may be used to quench thrombin activity upon extensive or limited action. Unlike heparin-antithrombin III complex which exclusively inhibits alpha-and gamma-thrombin, hirudin also inhibits meizothrombin, a precursor of alpha-thrombin. Thus, hirudin may be used for the detection of meizothrombin as well as for the prevention of its action in plasma samples. In conjunction with chromogenic substrates, hirudin may serve to discriminate between actions mediated by thrombin, its precursors, cofactors and effectors and actions of other enzyme systems. The principle of this hirudin application is exemplified for factor-V- and factor-VIII-dependent anticoagulant activity of protein C.