[Detection of Hemophilia A carrier state]

Factor VIII biological activity and factor-VIII-related antigen were measured in the plasma of 78 definite, probable or potential carriers of haemophilia A and in a control group of 74 normal women. Low values of factor VIII activity could be detected in 11 of 24 definite carriers, in 11 of 26 probable carriers and, in 10 of 28 potential carriers. On the other hand, the ratio of factor VIII activity to factor-VIII-related antigen was significantly lowered in 79 percent of definite carriers, in 50 percent of probable carriers and, in 21 percent of potential carriers. These studies indicate that determinations of both factor VIII activity and antigen is more reliable procedure in the detection of the carrier state for haemophilia A than determinations of factor VIII activity alone.