Objective    To study the environmental factors for inhibitor formation of factor Ⅷ in 215 Chinese patients with hemophilia A.     Methods    Formation

change and transformation of factor Ⅷ were observed in 215 Chinese patients with hemophilia A during the 2-year follow-up period from June 2007 to June 2009. The environmental factors for inhibitor formation of factor Ⅷ were retrospectively analyzed.     Results    The cumulative incidence of hemophilia A in the 215 Chinese patients during the 2-year follow-up period was 11.6% (25/215). Multivariate analysis showed that the risk for inhibitor formation of factor Ⅷ was lower in short-term low-dose preventive treatment than in on-demand treatment (OR=0.037

95%CI=0.002-0.616). The higher the severity of hemophilia was

the less the cumulative exposure day was

and the greater the risk for the inhibitor formation of factor Ⅷ was. Severe bleeding episodes was a high risk factor for the inhibitor formation of factor Ⅷ (OR=117.045

95%CI=19.333-708.617). Infusion forms and major infection events were not related with the inhibitor formation of factor Ⅷ.     Conclusion    Inhibitor formation of factor Ⅷ in Chinese patients with hemophilia A may be related to the severity of hemophilia

infusion treatment (preventive treatment or on-demand treatment)

cumulative exposure day and severe bleeding episodes in China at present.