Comparative measurement of anti-factor VIII antibody by Bethesda assay and ELISA reveals restricted isotype profile and epitope specificity.

Factor VIII (FVIII) inhibitor antibodies are produced against functional epitopes of FVIII in about 30% of severe hemophilia A patients leading to inhibition of its procoagulant activity. The Bethesda assay, the most commonly used method to measure FVIII inhibitors, based on inhibition of coagulant activity of FVIII, is neither able to detect noninhibitory antibodies nor their isotype. In this study we employed an indirect enzyme-linked immunosorbent assay (ELISA) to measure dif ferent isotypes and IgG subclasses of anti-FVIII anti body in the plasma of hemophiliacs (with and without inhibitor) and normal individuals using recombinant FVIII-coated microtiter plates.