Thrombin generation assay and its application in the clinical laboratory

BACKGROUND: A gap exists between in vivo and ex vivo coagulation when investigated by use of the coagulation tests prothrombin time (PT) and activated partial thromboplastin time (APTT). The thrombin generation assay (TGA) has been developed to fill this gap. CONTENT: TGA evaluates thrombin generation (resulting from the action of the procoagulant driver) and decay (resulting from the action of the anticoagulant driver), thus assessing the balance between the two. Coagulation of the test plasma (platelet poor or platelet rich) is activated by small amounts of tissue factor and phospholipids, and the reaction of thrombin generation is continuously monitored by means of a thrombin-specific fluorogenic substrate. Among the parameters derived from the thrombin-generation curve, the most important is the endogenous thrombin potential, defined as the net amount of thrombin that test plasmas can generate on the basis of the relative strength of the pro- and anti-coagulant drivers. TGA is therefore the candidate assay to investigate hypo- or hypercoagulability. SUMMARY: From my analysis of the literature, I draw the following conclusions. There is strong evidence that TGA is helpful to elucidate coagulation mechanisms in various clinical conditions that until recently were poorly understood (chronic liver disease; diabetes; inflammatory bowel disease, myeloproliferative neoplasms, nonalcoholic fatty liver disease). TGA is a promising laboratory tool for investigating hemorrhagic coagulopathies and monitoring replacement therapy in hemophiliacs, predicting the risk of recurrent venous thromboembolism after a first event, and monitoring patients on parenteral or oral anticoagulants. These applications require clinical trials in which TGA results are combined with specific clinical end points.