[Inhibitor hemophilia A--diagnostic and therapeutic significance of controlled substitutions with factor VIII]

10 haemophiliacs with constant low inhibitor levels to factor VIII (0.5-2.5 Bethesda units (BU) per ml) and 4 patients without antibodies were examined by a controlled substitution with factor VIII. We investigated the factor VIII in-vivo-recovery, the half disappearance time and the biological half-life. 4 different reaction patterns could be observed: 6 patients with antibodies showed the same recovery as those haemophiliacs without inhibitors but the half life was shorter. 2 inhibitor patients did not achieve the expected increments of factor VIII, but had normal half life. One patient had reduced recovery and shortened half life. Only in one patient (inhibitor levels 0.8-1.0 BU/ml) all parameters were in the normal range.