Distribution of Transferrin Saturations in the African-American
Population
Victor R. Gordeuk,
Christine E. McLaren,
Anne C. Looker,
Victor Hasselblad, and
Gary M. Brittenham
From the Department of Medicine, The George Washington University
Medical Center, Washington D.C.; the Department of Mathematics,
Moorhead State University, Moorhead MN; the Nutrition Statistics
Branch, National Center for Health Statistics, Hyattsville MD; the
Center for Health Policy Research and Education, Duke University,
Durham, NC; and the Department of Medicine, MetroHealth Medical Center,
Case Western Reserve University School of Medicine, Cleveland OH.
To determine if transferrin saturations in African Americans may
reflect the presence of a gene that influences iron metabolism, we
analyzed the distribution of these values in 808 African Americans from
the second National Health and Nutrition Survey. We tested for a
mixture of three normal distributions consistent with population genetics for a major locus effect in which the proportion of normal homozygotes is p2; of heterozygotes, 2pq;
of affected homozygotes, q2; and in which p+q
= 1. Three subpopulations based on transferrin saturation were
present (P < .0001) and the fit to a mixture of three normal
distributions was good (P = .2). A proportion of .009 was
included in a subpopulation with a mean ± standard deviation transferrin saturation of 63.4% ± 5.7% (postulated
homozygotes for a gene that influences iron metabolism), 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 consistent with
population genetics because the sum of the square roots of the
proportions with the lowest mean transferrin saturation (P = .925) and the highest (q = 0.093) was approximately 1 (1.018). The results are consistent with the presence in African
Americans of a common locus that influences iron metabolism.
Blood, Vol. 91 No. 6 (March 15), 1998:
pp. 2175-2179
© 1998 by The American Society of Hematology.
