Treatment Adherence in Haemophilia: Methods of Assessment, Clinical Outcomes, and Real‐World Evidence

BACKGROUND: Treatment adherence is widely regarded as a key determinant of therapeutic effectiveness in haemophilia; however, both its assessment and its clinical relevance remain highly variable across studies. AIM: This review aims to provide an overview of adherence to haemophilia treatments, focusing on assessment methodologies, reported adherence levels, and their relationship with clinical outcomes in real-world settings. METHODS: Evidence derived from surveys, validated adherence scales, dispensing-based metrics, and patient-reported data was examined. Clinical outcomes assessed included bleeding events, joint health, pain, and quality of life. RESULTS: Overall, adherence was generally reported as high, particularly among patients receiving prophylactic therapy. Nevertheless, substantial heterogeneity was observed in adherence definitions, measurement approaches, and outcome selection, limiting comparability across studies and complicating the interpretation of adherence-outcome relationships. CONCLUSIONS: While adherence is traditionally considered a prerequisite for treatment effectiveness, establishing a consistent and clinically meaningful association with outcomes remains challenging. Greater methodological standardization is needed to enhance the interpretability of real-world evidence and to better inform clinical and therapeutic decision-making in haemophilia. SUMMARY: Adherence to haemophilia treatment is assessed using heterogeneous methods Reported adherence levels are generally high across prophylactic regimens Associations between adherence and clinical outcomes are inconsistent Methodological standardization is needed to strengthen real-world evidence.