In vivo dissociation of factor VII (AHF) activity and factor VII-related antigen in von Willebrand's disease.

Using monospecific rabbit antihuman factor VIII antiserum, we have examined the amounts of factor VIII-related antigen and compared these to the levels of factor VIII procoagulant activity in normal subjects and patients with von Willebrand's disease. We have observed that even without transfusion all nine probands with von Willebrand's disease and 20 of their 34 relatives possessed a significantly elevated factor VIII activity/factor VIII-related antigen ratio when compared to that of 55 normal subjects. It is suggested that an elevated factor VIII activity/factor VIII-related antigen ratio may be used for detection of the carriers of von Willebrand's disease.