A Sudden Increase in Factor VIII Inhibitor Development in Multitransfused Hemophilia A Patients in The Netherlands

The development of antibodies to factor VIII (Inhibitors) in response to clotting-factor concentrates administration in hemophilia is common during the first few years of treat-ment but rare in multitransfused patients. We have inves-tigated the possible association of a recently introduced factor VIII concentrate (Factor VIII CPS-P) in The Nether-lands with the occurrence of Inhibitors. To this effect, we conducted two studies. First, we performed a national multicenter study in which clinical Information and Inhibitor test results were obtained for 447 hemophilia A patients over the period 1988 through 1991. Secondly, for a baseline comparison we estimated the frequency of Inhibitor de-velopment in a closely followed cohort of 144 patients, from 1984 through 1989. Before the introduction of Factor VIII CPS-P, the incidence of new Inhibitors was 4.4/1,000 pa