The detection of carriers of classic hemophilia. H. P. Smith Memorial Lecture.

The authors summarize their experience with detection of the carrier state in classic hemophilia. Their test depends upon the observation that the plasma of patients with classic hemophilia, deficient in functional antihemophilic factor, contains normal amounts of precipitating antigenic material. By inference, the plasma of carriers should be relatively deficient in functional antihemophilic factor, but should contain normal amounts of antihemophilic factor-like antigenic material. Data obtained from 81 obligate carriers suggest that at least 90% of these women can be identified as carriers in the laboratory by demonstrating that there is an excess of antihemophilic factor-like antigenic material in plasma relative to functional antihemophilic factor. Further, at least two-thirds of mothers of individuals with isolated cases of hemophilia are carriers, suggesting that mutation is a relatively rare cause of hemophilia. Only about one-third of daughters of carriers who had no sons can be identified as carriers, a result due to the systematic exclusion of those daughters who had already had a hemophilic son.