| Description: |
Factor VIII inhibitors (inactivating antibodies) occur in at least 10% to 15% of hemophiliacs as an alloimmune complication of factor VIII therapy. Autoimmune factor VIII inhibitors (also termed acquired hemophilia) have been described in postpartum women, with autoimmune diseases, antibiotic therapy, and in association with malignancy. The inhibitor assay measures the ability of dilutions of patient plasma to inhibit factor VIII activity in pooled normal plasma after a 2-hour incubation at 37°C. The inhibitor level (in Bethesda units) is calculated as the reciprocal of the patient dilution which inhibits 50% of the normal plasma factor VIII activity. For example, if a 1:10 dilution of patient plasma inhibits 50% of normal factor VIII activity, then the titer is 10 Bethesda units. |
