Inhibitor development against factor VIII (FVIII) is the most common complication of hemophilia A replacementtherapy. One of the variables considered to influence inhibitor development is the ABO blood group. Patients with blood groupO have, on average, a 30%–40% lower endogenous von Willebrand factor (VWF) concentration. It has been postulated that VWFlevels influence inhibitor development.
The objective of this study was to investigate the inhibitor risk in patients with severehemophilia A comparing those with blood group O with those with non-O blood groups.
The study population consisted of children with severe hemophilia A, born between 2000 and 2020, who reached 50FVIII exposure days in the PedNet registry. Inhibitors were considered to be clinically relevant when at least two consecutivemeasurements were tested positive.
Routine testing of blood groups varied between centres: Out of 1172 patients with severe hemophilia A, blood group statuswas known in 759 patients (65.8%). The relative risk of inhibitor development for blood group O in comparison to non-O was 1.04(95% CI: 0.7–1.7). In conclusion in the PedNet cohort, blood group O did not increase the risk of inhibitors in previously untreated children withsevere hemophilia A
Marloes de Kovel 1 Aimée-Claire van Haaster1 Manuel Carcao 2 Susanna Ranta3 Heidi Glosli 4Georges E. Rivard5 Gili Kenet 6 Karin Kurnik7 Christel Van Geet8 Manuela Carvalho9Nadine G. Andersson 10,11,12 Mutlu Kartal-Kaess13 Rolf Ljung11 H. Marijke van den Berg 1 the PedNet StudyGroup