Ecarin chromogenic assay - A new method for quantitative determination of direct thrombin inhibitors like hirudin

Abstract

A new sensitive and precise method for quantitative determination of direct thrombin inhibitors is described, the ecarin chromogenic assay (ECA). Ecarin is used as the specific prothrombin-activating principle. The cleavage of a chromogenic substrate by meizothrombin is inhibited in a concentration-dependent fashion by direct thrombin inhibitors. For the ECA, the linear measuring range is about 0.1-3.0 μg hirudin/ml plasma. Coefficients of variations between 2.3 and 4% over the whole concentration range were achieved. The ECA has proved to be more sensitive than the compared tests (ecarin clotting time and a thrombin-based chromogenic assay); a detection limit of 0.011 μg hirudin/ml and a quantitation limit of 0.032 μg hirudin/ml were calculated. The ECA is independent of the variations of the coagulation variables fi brinogen and prothrombin. Neither heparin nor oral anticoagulants interfere with the ECA. Copyright © 2004 S. Karger AG, Basel.