Carriers and noncarriers of haemophilia A: I. Multivariate analysis of pedigree data, screening blood coagulation tests and factor VIII variables.

From a material of 18 obligate carriers of haemophilia A and 40 healthy females, a discriminant function was created, based on ratio of factor VIII related antigen (electroimmunoassay = EIA) to factor VIII activity (one-stage assay), factor VIII related antigen (radioimmunoassay = RIA) and number of bleeding symptoms. The standard deviation of p-values for carrier- and non-carrier state (less than 0.05) was estimated by a procedure built on the 'jack-knife' method. By combined information of pedigree- and discriminant analysis data, 43 possible carriers were classified as carriers/noncarriers with about 95% confidence. Carriers were significantly older, had more bleeding symptoms, longer APTT, lower factor VIII activity, factor VIII procoagulant antigen, and higher ratio of factor VIII related antigen (EIA) to factor VIII activity (one-stage) and to factor VIII related antigen (RIA) respectively, than classified noncarriers. Individuals with blood group A, B, AB had significantly higher levels of factor VIII related antigen (EIA) and (RIA), and ristocetin cofactor, compared with blood group O. Obligate carriers with severe haemophilia A in their families had more bleeding symptoms than corresponding group with moderate haemophilia.