Limit of Detection and Threshold for Positivity of the Centers for Disease Control and Prevention Assay for Factor VIII Inhibitors

摘要

BackgroundThe Bethesda assay (BA) for measurement of factor VIII (FVIII) inhibitors called for quantitation of positive inhibitors using dilutions producing 25–75% residual activity (RA), corresponding to 0.4–2.0 Bethesda units, recommending use of “more sensitive methods” for samples with RA closer to 100%. The Nijmegen modification (NBA) changed the reagents used but not these calculations. Some specimens negative by NBA have been shown to have FVIII antibodies detectable by sensitive immunologic methods.