<unk>  <unk>  is a laboratory test used to monitor anticoagulation during treatment with hirudin, an anticoagulant medication which was originally isolated from leech saliva.<unk> , the primary reagent in this assay, is derived from the venom of the saw-scaled viper, Echis<unk> atus. In the clinical assay, a known quantity of<unk>  is added to the plasma of a patient treated with hirudin.<unk>  activates prothrombin through a specific proteolytic cleavage, which produces meizothrombin, a prothrombin-thrombin intermediate which retains the full molecular weight of prothrombin, but possesses a low level of procoagulant enzymatic activity. Crucially, this activity is inhibited by hirudin and other direct thrombin inhibitors, but not by heparin. The<unk>  is also unaffected by prior treatment with warfarin or the presence of phospholipid-dependent anticoagulants, such as lupus anticoagulant. Thus, the<unk>  is prolonged in a specific and linear fashion with increasing concentrations of hirudin. An enhancement of the<unk>  is the<unk>  chromogenic assay (ECA) in which diluted sample is mixed with an excess of purified prothrombin and the generated meizothrombin is measured with a specific chromogenic substrate. This assay shows no interference from prothrombin or fibrinogen in the sample and is suitable for the measurement of all direct thrombin inhibitors.
Ecarin clotting time
Thrombin time
Kaolin clotting time
Activated clotting time
Prothrombin time
Partial thromboplastin time
Thrombin generation assay
Activated protein C resistance test