Detection of Carriers for Factor IX (PTC) Deficiency

is a congenital, often familial, hemorrhagic disorder which was distinguished from classical hemophilia (AHG deficiency, factor VIII deficiency, hemophilia A) in 1952.13 Like the latter, it is usually inherited as a sex-linked recessive trait: only the male hemizygote for the abnormal gene is clinically affected, and the female heterozygote or carrier is asymptomatic. From a eugenic standpoint it would be of value to have a method which could distinguish carriers from noncarriers in factor IX deficiency kindreds. An occasional carrier has had a tendency to bruise or bleed somewhat more easily than do normal women, or has had an abnormality in some clotting test ( serum prothrombin time, partial thromboplastin time, thromboplastin generation test, or plasma factor IX assay ) , suggesting that at least some carriers may have a partial deficiency of factor IX. The purpose of this paper is to present the resubts of clotting tests performed on 14 carriers for factor IX deficiency, and to describe a new assay for factor IX. By means of this assay, 11 of the 14 were found to have subnormal factor IX activity.