Evaluation of a novel ELISA screening test for detection of factor VIII inhibitory antibodies in haemophiliacs.

Treatment of patients with haemophilia A with coagulation factor concentrates may result in the development of inhibitory antibodies directed against factor VIII (FVIII). In this study, a previously unpublished ELISA test for FVIII inhibitor screening (Genetic Testing Institute [GTI] FVIII inhibitor, Brookfield, WI, USA) was evaluated in 131 blood samples (124 samples from patients with haemophilia A, and seven serial samples from one patient with an acquired FVIII inhibitor). Comparisons were made with the routine screening assay (based on recovery of FVIII) and confirmed where positive (< 90% recovery) with the New Oxford assay. The ELISA kit had a sensitivity of 97.7% and specificity of 78.4%. The high negative predictive value of this new test (98.6%) suggests it may be useful as a reliable, rapid (< 2 h) and flexible (microwell strip format) tool for inhibitor screening of samples from both patients with haemophilia A and those with suspected acquired FVIII inhibitors.