Gaps Between Prescription and Practice: Pharmacy-Based Measurement of Prophylaxis Adherence in Haemophilia.

INTRODUCTION: Adherence to prophylactic replacement therapy is critical to prevent bleeding and joint damage in haemophilia. Although Brazil provides universal and free access to clotting factor concentrates (CFC) through the public health system, real-world adherence remains insufficiently explored. AIM: To assess adherence to prophylaxis and its association with bleeding outcomes in people with haemophilia A and B treated at two Haemophilia Treatment Centres (HTCs) in southeastern Brazil. METHODS: In retrospective observational study, 224 people with haemophilia receiving ≥12 months of FVIII or FIX prophylaxis in 2024 were included. Adherence was evaluated using pharmacy dispensing records by comparing expected annual prescribed CFC consumption with actual dispensed units. Patients were classified as optimal (<15% non-dispensed), suboptimal (15%-25%), or non-adherent (>25%). Annualized bleeding rate (ABR) and annualized joint bleeding rate (AJBR) were analyzed according to adherence status. RESULTS: Although the median factor dispensing rate was 73% (IQR: 47-96), this value falls below the 75% threshold, indicating a high overall prevalence of non-adherence. When patients were stratified into optimal, suboptimal, and non-adherent groups, 52% were classified as non-adherent. Non-adherence was more frequent in one centre (60.3% vs. 43.7%, p = 0.027) and among individuals aged 20-39 years (p = 0.003). Despite high objective non-adherence, median ABR and AJBR were zero across groups, although individual variability persisted, including bleeding events among adherent patients. CONCLUSION: Even within a universal-access health system, substantial gaps between prescribed and executed prophylaxis persist. Dispensing-based adherence assessment reveals hidden non-adherence and may support targeted multidisciplinary strategies to optimize long-term outcomes in haemophilia care.