Identifying Carriers of Mild Haemophilia

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Abstract
The problems of carrier identification in mild hemophilia were examined by studying a large kindred transmitting factor (F) VIII:C [procoagulant activity] levels which averaged 17 .mu./dl in affected males. Fifteen obligatory carriers and 13 normal women from this kindred were used as reference groups to produce a set of linear discriminants. The utility of these discriminants in identifying carriers of mild hemophilia was compared with that of a similar set of discriminants which had been prepared for use with carriers of severe hemophilia, each set of discriminants being tested against both data bases. Both sets of discriminants had large error rates when applied to the mild data base, and both had much smaller error rates when applied to the severe data base. This outcome resulted from the greater overlap between the F VIII-related activities of mild carriers and normal women than the overlap of these activities between severe carriers and normal women. Correct classification of many but not all women from families of mild hemophilia would apparently be difficult. Discriminants prepared using obligatory carriers of severe hemophilia were not more inefficient in mild hemophilia than those prepared using obligatory carriers of mild hemophilia. A single set of discriminants prepared from reference groups of normal women and obligatory carriers of severe hemophilia may be used for identifying potential carriers of all grades of hemophilia. Statistically speaking F VIIIR:Ag [F VIII related antigen] assays provide a limited amount of information for this purpose.