Factor 8 detection by hemagglutination inhibition: hemophilia A and von Willebrand's disease.

Factor VIII activity was detected immunologically in both the serums and plasmas of 14 normal individuals and 14 patients with hemophilia A. A hemagglutination-inhibition test with rabbit antibody to highly purified (10,000-fold) factor VIII from humans was used. Serums and plasmas from eight patients with von Willebrand's disease showed little or no factor VIII activity in this test, an indication that the test may serve as a specific assay for differentiation between von Willebrand's disease and hemophilia A.