Factor VIII-Related Antigen and von Willebrand's Disease

Immunological methods for the detection and assay of factor VIII-related antigen have proved to be valuable tools in the study of factor VIII, haemophilia and von Willebrand's disease. The antibody neutralization tests, with their inherent difficulties and variability, have been largely replaced by the electroimmunoassay based on the method of Laurell. Using this latter method, it has been convincingly shown that whereas normal individuals and haemophiliacs have an antigen which precipitates with the rabbit anti-factor VIII antibody, patients with von Willebrand's disease have a reduced amount of the antigen.
The relationship of the antigen to factor VIII activity is not yet clear; nevertheless the assay of factor VIII-related antigen is proving of some value in the diagnosis of von Willebrand's disease and in the detection of carriers of haemophilia. In von Willebrand's disease the test for the antigen along with the ristocetin test for platelet aggregation has thrown new light on the condition and has helped to define several variants of the disease.