Hemophilia prophylaxis adherence and bleeding using a tailored, frequency‐escalated approach: The Canadian Hemophilia Primary Prophylaxis Study

BACKGROUND: Standard of care for persons with severe hemophilia A includes regular replacement of factor VIII (FVIII). Prophylaxis regimens using standard half‐life (SHL) FVIII concentrates, while effective, are costly and require frequent intravenous infusions. AIM: This study evaluated the adherence of 56 boys with severe hemophilia A to tailored, frequency‐escalated prophylaxis with an SHL recombinant FVIII concentrate. METHODS: We reviewed the factor infusion and bleeding logs of study subjects. Adherence to the prescribed regimen was calculated on a weekly basis, and bleeding rates were determined from self/proxy‐reported bleeding logs. The primary outcome was adherence to the prescribed prophylaxis regimen. RESULTS: The median (range of values [ROV]) weekly adherence to prophylaxis was 85.7% (37.4%‐99.8%). The median (ROV) adherent weeks on steps 1 (weekly), 2 (twice weekly), and 3 (alternate‐day) were 92.9% (50%‐100%), 80.3 (32%‐96%), and 72.6% (14%‐98%); relative to step 1, subjects were less likely to be adherent on steps 2 and 3 (P < 0.00). On step 1, our cohort had higher adherence than previously reported rates. The median (ROV) adherence to the breakthrough bleeding protocol was 47.1% (0%‐100%). At any given time, bleeding risk was reduced by 15% for each 10% increase in adherence during the preceding 12 weeks (hazard ratio, 0.85; 95% confidence interval, 0.81‐0.90). CONCLUSION: This cohort had high rates of adherence to the prescribed prophylaxis regimen. Initiating prophylaxis with once‐weekly infusions facilitated adherence to the prophylaxis regimen in this cohort of boys with severe hemophilia A started on primary prophylaxis at a very young age.