OBJECTIVETo study the incidence and characteristics of coagulation factor VIII (FVIII) inhibitor development in Chinese patients with hemophilia A.

METHODSA 24-month continuous follow-up was conducted among 215 Chinese patients with hemophilia A to observe the characteristics of FVIII inhibitor development and the clinical characteristics of the patients.

RESULTSThe cumulative incidence of FVIII inhibitor development in 24 months was 11.6% (25/215) in these patients. Of the 25 patients with FVIII inhibitor development, 18 (72%) had low-titer inhibitors and 7 (28%) had high-titer inhibitors. The patients developed the inhibitors after a median of 150 exposure days at a median age of 25 years (6-59 years). Fifteen patients with low-titer inhibitors (median 1.25 BU/ml) showed gradual disappearance of the inhibitors in a median of 10 months (6-15 months) without any treatment, and 5 patients with high-titer inhibitors (median 100 BU/ml) remained positive in 24 months; the other 5 FVIII inhibitor-positive cases showed no significant changes. In the 25 patients developing FVIII inhibitors, the bleeding frequency increased significantly (P=0.025), and in 18 of the patients who continued to use FVIII products, a significant increase in the dose of medication was noted (P=0.015), but the number of target joints did not increase in 24 months (P=0.329).

CONCLUSIONThe incidence and characteristics of factor VIII inhibitor development differ between Chinese patients with hemophilia A and those in developed countries.