Thrombin Generation Assay to Support Hematologists in the Era of New Hemophilia Therapies

Hematology laboratories have traditionally monitored hemophilia replacement therapy by measuring coagulation factors before and after infusion. However, new drugs that do not rely on the replacement of the deficient factor require new approaches to laboratory monitoring, as factor VIII (FVIII) or factor IX (FIX) assays are no longer adequate. Non-factor therapies come in many different forms, that have one thing in common: they all increase thrombin generation. Their main adverse effect is thrombosis which may occur when too much thrombin is formed. This is the perfect mirror image of anticoagulant treatment, which always diminishes the amount of thrombin formed and has bleeding as its main adverse effect. Thrombin-forming capacity is decreased in congenital bleeding disorders and increased in prothrombotic conditions, indicating it governs bleeding and thrombosis. Therefore, the thrombin generation assay (TGA) is a logical tool for monitoring non-factor therapies, offering a comprehensive assessment of hemostatic balance. TGA identifies patients with severe bleeding, helps to optimize bypassing therapy, and detects hypercoagulability, making it ideal for guiding and monitoring hemophilia treatment with non-factor therapies. It also assesses the efficacy and safety of combined therapies, including non-factor therapies with bypassing agents or FVIII/FIX concentrates. The purpose of this paper is to review the current state of knowledge regarding the use of TGA to monitor novel hemophilia therapies. It will address controversies, limitations, and knowledge gaps related to the integration of TGA into personalized medicine in routine clinical practice.