The most specific tool for the Direct Thrombin Inhibitors (DTIs) assay
Parenteral DTIs (e.g. argatroban, bivalirudin, hirudin) are increasingly used for anticoagulation in several clinical situations, such as treatment of unstable angina undergoing percutaneous coronary angioplasty and treatment of patients with HIT. Oral DTIs such as dabigatran are now widely used for various indications, including for thrombosis prophylaxis in atrial fibrillation.
In contrast to classical anticoagulants, DTIs have an immediate onset of action, do not require plasmatic cofactors, inhibit clot bound thrombin, and do not induce HIT. There is no specific antidote for DTIs.
The ecarin chromogenic assay (ECA) is a promising tool for determining the exact concentration of DTIs in plasma. This method is an enhancement of the well established ecarin clotting time (ECT): ecarin converts prothrombin, present in excess in the reagent, into meizothrombin. The cleavage of a chromogenic substrate by prothrombin activation products is inhibited by DTIs. Thus, the generation of pNA is inversely proportional to the concentration of the DTI in the plasma.
Unlike the aPTT, ECA is completely independent of the concentration of coagulation factors or plasmatic inhibitors in the sample. Additionally, it is not influenced by lupus anticoagulants allowing for a specific determination. ECA is completely insensitive to heparin, LMWH, danaparoid, fondaparinux and direct factor Xa antagonists. This facilitates bridging and transition to other anticoagulants and specifically dosage adaptation in high risk patients. Importantly, unlike several other assays, the dose response is linear and does not show a plateau at elevated concentrations.
ECA can be adapted to all fully automated Stago instruments and features a wide measuring range with excellent precision. The ECA range includes 2 reagent formats dedicated to each type of DTIs: ECA-H for recombinant hirudins (Cat. Nr. 1051) and ECA-T for synthetic DTIs (Cat. Nr. 1052). Specific standards and controls are also available.