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Objective: The primary objective of this study was to assess whether there are different patterns (classes) of joint health in young boys with severe haemophilia A (SHA) prescribed primary tailored prophylaxis. We also assessed whether age at first index joint bleed, blood group, FVIII gene abnormality variant, factor VIII trough level, first‐year bleeding rate and adherence to the prescribed prophylaxis regimen significantly predicted joint damage trajectory, and thus class membership. Methods: Using data collected prospectively as part of the Canadian Hemophilia Primary Prophylaxis Study (CHPS), we implemented a latent class growth mixture model technique to determine how many joint damage classes existed within the cohort. We used a multinomial logistic regression to predict the odds of class membership based on the above predictors. We fitted a survival model to assess whether there were differences in the rate of dose escalation across the groups. Results: We identified three distinct classes of trajectory: persistently low, moderately increasing and rapidly increasing joint scores. By multinomial regression, we found that only age at first index joint bleed predicted rapidly increasing joint scores. The rapidly increasing joint score class group moved through dose escalation significantly faster than the other two groups. Conclusions: Using tailored prophylaxis, boys with SHA follow one of three joint health trajectories. By using knowledge of disease trajectories, clinicians may be able to adjust treatment according to a subject's predicted long‐term joint health and institute cost‐effective programmes of prophylaxis targeted at the individual subject level. [ABSTRACT FROM AUTHOR]

Introduction: In many countries, there is a shift from standard half‐life (SHL) to extended half‐life (EHL) clotting factor concentrates (CFCs). Aim: To describe the experience of switching from SHL to an EHL FVIII CFC and the impact of this on frequency of infusions, factor consumption, bleeding rates and HRQoL using the Canadian Hemophilia Kids' Life Assessment Tool (CHO‐KLAT). Methods: A retrospective chart review was conducted at a single haemophilia treatment centre in 2018 that included boys (ages: 4‐18 years) with moderate/severe haemophilia A, without inhibitors, who switched from a SHL to an EHL FVIII CFC in the previous 2 years and for whom HRQoL data were available. Results: The study cohort comprised 38 boys [mean (SD) age: 11.0 (3.4) years] with moderate (n = 5)/severe (n = 33) haemophilia A. The switch was associated with a 33% reduction in the number of weekly infusions from a median of 3.5 to 2.3 (P <.0001) and a 17% reduction in median FVIII consumption from 103 IU/kg/wk to 85.5 IU/kg/wk (P =.004). There was no significant change in annualized joint bleed rates or in CHO‐KLAT scores. Conclusions: Despite documenting several benefits of switching to EHL FVIII (less infusions, lower factor consumption with no increase in bleeding), our study did not demonstrate any improvement in HRQoL. We conclude that either the current CHO‐KLAT tool is not optimized to measure burden of treatment administration in boys with low bleed rates switching from SHL to EHL FVIII CFCs or that a reduction of 1.2 infusions/week does not result in a meaningful change in HRQoL. [ABSTRACT FROM AUTHOR]