Residual FVIII against a sample dilution for a type 1 inhibitor often seen in congenital hemophilia (pink line) and against the type 2 inhibitor seen in a clinical case (black line). The blue shaded area denotes the area between 30% and 70% residual FVIII, where the Bethesda assay is considered to be accurate. For type 1 inhibitors, only 1 or 2 dilutions will give interpretable results (and the same calculated titer), whereas for type 2 inhibitors, multiple dilutions will give interpretable results, and the calculated titer will be different for each one.