Relationship of factor IX antigen and coagulant in hemophilia B patients and carriers
Pechet, L.; Tiarks, C.Y.; Stevens, J.; Sudhindra, R.R.; Lipworth, L.
Thrombosis and Haemostasis 40(3): 465-477
1979
ISSN/ISBN: 0340-6245 PMID: 425061 Document Number: 149437
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 concordant (ratios .gtoreq. 0.71) or discordant (< 0.71). The diagnostic classification into concordant and discordant patterns was difficult in patients with low levels of antigen where the 2 forms may merge due to the insensitivity of the assay below 12%. Of the total cases studied, 36% were discordant (excess antigen). This was in agreement with 33.66%, a composite figure representing 199 cases described in 5 recently published papers, and indicated that approximately 1/3 of the hemophilia B population was of the discordant type. The pattern, when established, was consistent in each kinship studied. Crossed antigen-antibody electrophoresis did not reveal any abnormalities in the hemophilia B plasmas with measurable IX-Ag. A low incidence of the BM variety was found. 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.