Factor VIII products and inhibitor development in severe hemophilia A

For previously untreated children with severe hemophilia A, it is unclear whether the type of factor VIII product administered and switching among products are associated with the development of clinically relevant inhibitory antibodies (inhibitor development). We evaluated 574 consecutive patients with severe hemophilia A (factor VIII activity, <0.01 IU per milliliter) who were born between 2000 and 2010 and collected data on all clotting-factor administration for up to 75 exposure days. The primary outcome was inhibitor development, which was defined as at least two positive inhibitor tests with decreased in vivo recovery of factor VIII levels. Inhibitory antibodies developed in 177 of th…