Thrombin Generation Assays in Clinical Hemostasis: From Mechanistic Insights to Clinical Applications

Thrombin plays a central role in hemostasis, serving as both the primary enzyme driving fibrin formation and the central regulator of anticoagulant pathways. Routine coagulation assays, such as prothrombin time and activated partial thromboplastin time, capture only a limited fraction of thrombin's role, overlooking inhibitory pathways and downstream regulation. Thrombin generation assays (TGAs) provide a global view of coagulation, measuring both formation and inhibition of thrombin over time. TGAs generate thrombin activity curves, from which parameters such as lag time, peak thrombin, time to peak, velocity index, and endogenous thrombin potential are derived. These parameters reflect hyper- or hypocoagulability and have been linked to clinical outcomes. Applications include monitoring anticoagulant therapy and reversal strategies, predicting venous thromboembolism recurrence, assessing thrombotic risk in cardiovascular disease and antiphospholipid syndrome, and stratifying bleeding risk in bleeding disorders. TGAs can also evaluate the efficacy of bypassing agents and novel hemostatic drugs in ex vivo settings. Barriers include technical complexity, preanalytical variability, and lack of standardization across laboratories. TGAs provide a global assessment of coagulation, demonstrating added value in both hyper- and hypocoagulable states. While most data remain research-based, growing evidence supports their utility in thrombotic risk prediction and bleeding risk assessment. Wider adoption in clinical practice will depend on assay standardization, validation in multicenter studies, and integration into clinical decision-making pathways.