Immunoradiometric assay of procoagulant factor VIII antigen (VIIICAG).

An immunoradiometric assay of procoagulant factor VIII antigen was developed using a human antibody to the procoagulant activity of factor VIII (VIII:C). The assay measures specifically the antigen related to factor VIII procoagulant activity (VIIICAG) both in plasma and in serum. VIII:C and VIIICAG were measured in a group of healthy individuals and in a group of haemophilia A patients. In haemophilia A at least four groups can be recognised on the basis of the presence or absence of VIII:C and VIIICAG and the VIII:C/VIIICAG ratio.