Titers of FVIII-specific antibodies assessed for individual immunoglobulin isotypes and IgG subclasses. Presented are the results of all plasma samples that contained FVIII-specific antibodies with a titer ≥1:80 of at least 1 immunoglobulin isotype or IgG subclass. (A) Twenty-four of 24 patients with severe hemophilia A and FVIII inhibitors (HA-INH). (B) Four of 77 patients with severe hemophilia A without FVIII inhibitors (HA-noINH). (C) Nineteen of 19 patients with acquired hemophilia A (Acqu-HA). (D) Seventeen of 634 healthy individuals (Healthy). A titer of 1:20 represents the screening cutoff of the method to differentiate positive and negative samples. The dotted line at a titer of 1:80 represents the lower limit of detection for FVIII-specific antibodies.3 Circles depict positive results for FVIII-specific antibodies; triangles represent results that were below the lower limit of detection for FVIII-specific antibodies. ND, not detectable.
