[Ecarin chromogenic assay: an innovative test for quantitative determination of direct thrombin inhibitors in plasma]

The ecarin chromogenic assay (ECA) was developed for quantitative determination of direct thrombin inhibitors. As a further development of the ecarin clotting time (ECT), the ECA is based on the same principle, the activation of prothrombin by ecarin a snake venom from Echis carinatus. In the ECA the prothrombin activation products meizothrombin and meizothrombin-desF1 cleave a chromogenic substrate, whereas in the clotting assay ECT plasma fibrinogen is converted to fibrin. The activity of meizothrombin/meizothrombin-desF1 is inhibited in a concentration-dependent fashion by direct thrombin inhibitors. The ECA can be used as ECA-H for quantitative determination of hirudin and as ECA-T for determination of synthetic thrombin inhibitors. As shown for hirudin, argatroban and melagatran, the ECA turned out as a very precise and sensitive method, which combines the advantages of ECT with those of chromogenic assays. In ECA very low interindividual variations were found compared to aPTT and even ECT. The ECA is independent of the variations of the coagulation variables prothrombin and fibrinogen.