Individualizing Hemophilia Prophylaxis Using Thromboelastography

This is a pilot study in children and adults with severe hemophilia A that utilizes the TEG/ROTEM to personalize their prophylaxis treatment. Primary objectives: • Assess the feasibility of TEG/ROTEM-guided modification of the current prophylaxis regimen for individuals with severe hemophilia A. Specifically, to: * Test and refine the operational protocol for using TEG/ROTEM to guide factor dosing * Estimate the proportion of hemophilia A patients whose dose will be modified based on TEG/ROTEM results * Monitor short term safety of patients whose dose has been modified. Secondary objectives * Perform thrombin generation assays to provide additional evidence supporting the TEG/ROTEM-guided dosing. * Obtain preliminary data on the economic impact of TEG/ROTEM-guided hemophilia A dosing regimens. * Obtain preliminary data on the potential improvement of subject/family burden resulting from TEG/ROTEM-guided regimen using generic and specific quality of life tools. The study period will consist of screening, pharmacokinetic (PK) study and follow-up. For subjects whose prophylaxis treatment regimen is modified, the follow-up period will include 3 follow-up clinic visits and 4 follow-up phone calls; these patients will remain on study for approximately 6 months following completion of the PK-study then will have an end of the study visit (visit 9). Subjects whose treatment regimen is not altered will end their study participation after Visit 2 and continuing with their current prophylaxis regimen. Study endpoints: A safety review will be conducted after the first 6 subjects complete 30 days with the extended prophylaxis treatment. If no safety issues are identified, the study will proceed, and second safety review will be after an additional 8 subjects complete 30 days of extended treatment. If a subject has two or more spontaneous bleeds in 30 days, the subject will be removed from the study. For subjects who did not have bleeds and completed at least 6 months of the study, ongoing prophylactic treatment will be decided by their treating physician.