F8 and hemophilia A: In conclusion, in our cross-sectional study consisting of 788 persons, we identified non-neutralizing FVIII-specific antibodies in a relatively large proportion of a nationwide population of persons with all severities of hemophilia A. Interestingly, IgG4 subclass antibodies were only observed in persons with a reported history of FVIII inhibitor and in those with a current (very-low titer) inhibitor.