Reference Values for the Haemophilia Joint Health Score in Patients With Severe Haemophilia Derived From the Canadian Bleeding Disorder Registry

BACKGROUND: People with haemophilia (PwH) are at increased risk of joint bleeding, often leading to haemophilic arthropathy. The Haemophilia Joint Health Score (HJHS) is widely used to evaluate joint health, but its interpretability is limited by the lack of age-based reference values. OBJECTIVE: This study aimed to develop national reference values for the HJHS in individuals with severe haemophilia using data from the Canadian Bleeding Disorder Registry (CBDR). METHODS: This cross-sectional study used CBDR data from 1 January 2018 to 31 December 2024. Participants aged ≥4 years with severe Haemophilia A or B and at least one HJHS score were included. Generalised Additive Models for Location, Scale, and Shape (GAMLSS) were used to estimate reference percentiles. Model performance was assessed using 100-fold cross-validation. RESULTS: A total of 551 participants with severe haemophilia were included, comprising 255 paediatric (<18 years of age) and 296 adult patients (mean age: 24 ± 17 years; range: 4-75; 87% with Haemophilia A). Reference percentiles (fifth to 95th) were generated for ages 4-70 years, demonstrating a positive association between age and HJHS scores. Cross-validation showed acceptable model consistency. CONCLUSION: This study provides the first national age-based reference values for the HJHS in individuals with severe Haemophilia A and B. These values allow clinicians to interpret joint health scores relative to age-specific expectations. Future research should extend age-specific HJHS reference values to additional national registries to strengthen global interpretation and comparison of joint health outcomes.