DISTRIBUTION OF TRANSFERRIN SATURATIONS IN THE AFRICAN-AMERICAN POPULATION

To determine if transferrin saturations in African Americans may refle ct the presence of a gene that influences iron metabolism, we analyzed the distribution of these values in 808 African Americans from the se cond National Health and Nutrition Survey. We tested for a mixture of three normal distributions consistent with population genetics for a m ajor locus effect in which the proportion of normal homozygotes is p(2 ); of heterozygotes, 2pq; of affected homozygotes, q(2); and in which p+q = 1. Three subpopulations based on transferrin saturation were pre sent (P < .0001) and the fit to a mixture of three normal distribution s was good (P = .2). A proportion of .009 was included in a subpopulat ion with a mean +/- standard deviation transferrin saturation of 63.4% +/- 5.7% (postulated homozygotes for a gene that influences iron meta bolism), while a proportion of .136 had an intermediate saturation of 38.0% +/- 5.7% (postulated heterozygotes) and .856 a saturation of 24. 6% +/- 5.7% (postulated normal homozygotes), These proportions were co nsistent with population genetics because the sum of the square roots of the proportions with the lowest mean transferrin saturation (P = .9 25) and the highest (q = 0.093) was approximately 1 (1.018). The resul ts are consistent with the presence in African Americans of a common l ocus that influences iron metabolism. (C) 1998 by The American Society of Hematology.