Relationship of Factor IX Antigen and Coagulant in Hemophilia B Patients and Carriers

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Abstract
A neutralizing and precipitating monospecific antiserum to human factor IX was developed. Plasmas from 224 hemophilia B patients, 39 obligatory and 38 possible carriers were studied by coagulant assays and Laurell’s electroimmunoassays. Based on factor IX coagulant (IX-C) to IX antigen (IX-Ag) ratios, the patients were classified as being either concordant (ratios ≥0.71) or discordant (M variety. Determining this type of hemophilia B did not appear to increase the degree of predictability of the carrier state. Studies of carriers demonstrated that immunologic techniques did not contribute to the predictability of the carrier state in pedigrees of the concordant variety. In the discordant group a factor IX-C/IX-Ag ratio of 0.7 or less indicated that a female was very likely to be a carrier. An improvement in the prediction of the carrier state in females of the discordant pattern was demonstrated.