Measurement of factor VIII procoagulant antigen in normal subjects and in hemophilia A patients by an immunoradiometric assay and by an enzyme-linked immunosorbent assay.

ABSTRACT

Factor VIII coagulant antigen (FVIIIAg) and FVIII coagulant activity (FVIIIC) were measured in 102 healthy individuals, in 5 hemophilia A carriers and in 21 hemophilia A patients before and after infusion of heat-treated high-purity FVIII concentrates. Factor VIIIAg was determined by a solid-phase micro enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies and by a conventional solid-phase immunoradiometric assay (IRMA). Factor VIIIC was assessed using a one-stage assay. The micro ELISA was decidedly more precise than the IRMA. There was a close correlation between the results obtained by the three assays in the plasma of healthy subjects and in hemophilia A carriers. After transfusion of FVIII concentrates to hemophilia A patients, the FVIIIAg recoveries were significantly lower than the FVIIIC recoveries and the biological half-life of FVIIIAg was significantly shorter than for FVIIIC. The calculated half-life of FVIIIC was longer than in any previous study.