Effect of ABO blood group on haemostatic parameters in severe haemophilia A patients performing acute moderate-intensity exercise.

: The primary objective was to assess the effect of ABO blood group on von Willebrand factor (VWF) rise induced by four bouts of moderate-intensity physical activity, on pharmacokinetics of a B-domain-deleted recombinant FVIII (BDD-rFVIII), and haemostatic parameters in severe haemophilia A patients with a null mutation. The secondary objective was to compare the response to exercise according to infused product type in a subgroup of patients who previously participated to the same exercise protocol, while treated with a full length recombinant FVIII (FL-rFVIII). Twenty patients had two visits (rest and exercise). Blood samples were drawn before administration of BDD-rFVIII and at 6 time points, until 24 h postinfusion. FVIII activity increased transiently by 1.1-fold, but only after the first exercise session, as compared to rest. VWF:Ag and platelet count were significantly elevated after each session. Mean FVIII half-life and thromboelastography measurements were unchanged with exercise. However, 14 participants had a slight variation of FVIII half-life with exercise compared to rest (from -3.42 h to +2.51 h). Seven patients demonstrated a longer FVIII half-life (four with O blood group), whereas the remainders had a reduced half-life (three with O blood group). FVIII half-life correlated with baseline VWF:Ag at rest (r = 0.70, P < 0.001) and with exercise (r = 0.67, P < 0.002). Recovery was different between FL-rFVIII and BDD-rFVIII at rest (P = 0.032), but no significant differences were observed between half-life of products at rest and with exercise. ABO blood group and the type of rFVIII administered did not influence the response to exercise.