ANTI-HEMOPHILIC GLOBULIN LEVELS IN CARRIERS OF HEMOPHILIA A*

Abstract

Plasma anti-hemophilic globulin (AHG) levels were measured in 35 obligatory carriers of hemophilia A and in 30 normal women by the Pool-Robinson assay technique. The normal women had a mean value of 92% of our reference plasma (range 52-133%). The carriers had a mean value of 58% (range 22 to 135%). Both sets of data appeared to be normally distributed when log per cent AHG was plotted on probability paper. AHG levels did not vary with the phase of the menstrual cycle. One carrier with 22% AHG had experienced clinically significant bleeding. Seven carriers with AHG levels between 30 and 40% had not bled abnormally. The distribution of AHG values in our carrier series suggests that AHG levels low enough to predispose to bleeding, i.e., below 30%, should occur in about 20 carriers per 1,000. Probability calculations indicate that the Pool-Robinson AHG assay will detect with reasonable accuracy (4 chances out of 5) about 75% of the true carriers in a potential carrier population and about 66% of the normal members in a potential carrier population. However, a potential carrier with even a very high AHG level still retains 1 chance in 5 of being a true carrier.