A Radial Immunodiffusion Method for the Assay of Factor VIII:C Antigen (VIII:C Ag) in Plasma

Publisher Website
Google Scholar
Abstract
A method was developed for the immunological quantitation of factor VIII:C Ag [factor VIII coagulative active site antigen] using a medium titer (50 new Oxford units) factor VIII:C antibody arising in a severe multitransfused hemophiliac. The method, which utilizes clotting inhibition in an agarose gel medium, gave close and significant correlation with the 2-stage factor VIII:C procoagulant assay (r = 0.83, P < 0.01) for 54 normal subjects. Similar or higher values were found in 19 mild, moderate and severe hemophiliacs with 2-30% average normal plasma levels of factor VIII:C (r = 0.72, P < 0.01). Four mild von Willebrand patients had similar results by immunoassay and procoagulant assay methods. A previously identified patient with cross-reacting material (CRM+) gave an immunoassay within the normal range (66%) with only 4% VIII:C activity detectable. The method offers a simple, sensitive and apparently reliable procedure for the plasma factor VIII:C Ag assay which may prove useful in the further investigation of factor VIII:C Ag and antibody heterogeneity. The procedure offers an alternative to immunoradiometric assay and may be of potential use in the assessment of the hemophilia carrier state and possibly early thrombosis detection.