Abstract
Laboratories monitor hemophilia replacement therapy by specific coagulation factor measurement before and after the infusion of human-derived or recombinant factors. Bypassing agents are now used for patients with inhibitors. Recently, modified long-acting coagulation factors have been introduced, for which discrepant results may be expected when the measurement is performed with one-stage clotting or chromogenic assays. Currently, novel drugs not based on coagulation factors are being developed and further tested in clinical studies. These drugs do require new methods, and therefore, laboratory evaluation of hemophilia will undergo dramatic changes in the near future. Accordingly, present laboratory methods for monitoring, which include one-stage clotting or chromogenic assays, used to measure either factor VIII (FVIII) or factor IX (FIX), will not be sufficient. A thrombin generation test (TGT) or thromboelastometry may be used to monitor bypassing agents. For measuring modified long-acting coagulation factors, chromogenic assays will be probably more suitable than one-stage clotting assays. Novel drugs that are not based on coagulation factors, such as emicizumab, fitusiran, or concizumab, will require alternative methods.