thrombin generation assay thrombin generation assay a thrombin generation assay (tga) or thrombin generation test (tgt) is a global coagulation assay (gca) and type of coagulation test which can be used to assess coagulation and thrombotic risk. it is based on the potential of a plasma to generate thrombin over time, following activation of coagulation via addition of phospholipids, tissue factor, and calcium. the results of the tga can be output as a thrombogram or thrombin generation curve using computer software with calculation of thrombogram parameters. thrombin generation assaysynonymstga; thrombin generation test; tgttest ofthrombin generation, coagulation, hypercoagulability tgas can be performed with methods like the semi-automated calibrated automated thrombogram (cat) (2003) or the fully-automated st genesia system (2018). tgas were first used as manual assays in the 1950s and have since become increasingly automated. parameters tga thrombogram (thrombin generation curve) parameters. etp is the endogenous thrombin potential or area under the curve. thrombogram parameters for the tga include: lag time (minutes; time until thrombin first generated/thrombin concentration first increased) time to peak or ttpeak (minutes; time to maximum concentration of thrombin generated) start tail (minutes; time at which thrombin generation ends and all generated thrombin has been inhibited) peak height or peak thrombin (molar concentration (e.g., nm) of thrombin; peak or maximum concentration of thrombin generated) velocity index (slope of thrombin generation between lag time/first thrombin generation and time to peak; corresponds to first derivative of this part of curve) endogenous thrombin potential (etp; area under the curve of the thrombin generation curve) etp-based apc resistance test