A cross-sectional follow-up study of physical activity in adults with moderate and severe haemophilia.

AIM: To conduct a cross-sectional follow-up assessment of physical activity (PA) in people with moderate and severe haemophilia (PwMSH) from the Irish Personalised Approach to the Treatment of Haemophilia (iPATH) study. METHODS: Between June-December 2021, participants' PA was measured over one week using accelerometery, and was compared with their previously measured data from the original iPATH assessment. Self-awareness of PA and the impact of the Covid-19 pandemic on PA, pain, mobility and function were retrospectively examined using a survey. RESULTS: Of 30 participants who returned surveys [n = 19, severe (FVIII, <.01 IU/mL); n = 4, moderate (FVIII, .01-.05 IU/mL); n = 7, severe (FIX, <.01 IU/mL); age: 47 (36, 55) years], 28 completed accelerometery (follow-up time: 3 years). There were no significant differences in accelerometer PA (all p > .05), but achievement of World Health Organisation guidelines increased (67.9%-75.0%; p = .646). Increased self-awareness of PA was reported by 76.7%, and 66.7% reported desires to become more physically active. Compared to normal, most reported either no differences or lower levels of PA during lockdown restrictions. Self-reported PA increased for most when restrictions eased from April 2021 onwards. Beyond the pandemic, concerns included pain and access to exercise resources. CONCLUSION: Self-reported PA throughout the pandemic was variable, whilst there were no significant differences in objectively measured PA between assessment periods, despite reports of increased self-awareness and desires to be physically active at follow-up. Further qualitative research is needed to design personalised PA and health interventions, capturing perspectives of patients, their families, and multi-disciplinary haemophilia healthcare providers.

Heterogeneity in the half-life of factor VIII concentrate in patients with hemophilia A is due to variability in the clearance of endogenous von Willebrand factor.

BACKGROUND: Previous studies have reported marked interindividual variation in factor VIII (FVIII) clearance in patients with hemophilia (PWH) and proposed a number of factors that influence this heterogeneity. OBJECTIVES: To investigate the importance of the clearance rates of endogenous von Willebrand factor (VWF) compared with those of other FVIII half-life modifiers in adult PWH. METHODS: The half-life of recombinant FVIII was determined in a cohort of 61 adult PWH. A range of reported modifiers of FVIII clearance was assessed (including plasma VWF:antigen and VWF propeptide levels; VWF-FVIII binding capacity; ABO blood group; and nonneutralizing anti-FVIII antibodies). The FVIII-binding region of the VWF gene was sequenced. Finally, the effects of variation in FVIII half-life on clinical phenotype were investigated. RESULTS: We demonstrated that heterogeneity in the clearance of endogenous plasma VWF is a key determinant of variable FVIII half-life in PWH. Both ABO blood group and age significantly impact FVIII clearance. The effect of ABO blood group on FVIII half-life in PWH is modulated entirely through its effect on the clearance rates of endogenous VWF. In contrast, the age-related effect on FVIII clearance is, at least in part, VWF independent. In contrast to previous studies, no major effects of variation in VWF-FVIII binding affinity on FVIII clearance were observed. Although high-titer immunoglobulin G antibodies (≥1:80) were observed in 26% of PWH, these did not impact FVIII half-life. Importantly, the annual FVIII usage (IU/kg/y) was significantly (p = .0035) increased in patients with an FVIII half-life of <12 hours. CONCLUSION: Our data demonstrate that heterogeneity in the half-life of FVIII concentrates in patients with hemophilia A is primarily attributable to variability in the clearance of endogenous VWF.