To the Editor.—
The recent article by Reed and Diehl1 shows clearly the difference in mean corpuscular volume (MCV) between white and black volunteer soldiers and notes the historical 7% to 8% incidence of heterozygous α and β-thalassemia in blacks. However, α-thalassemia is by far the most common in blacks, and most cases are α2- (one-deletion) thalassemia. These patients do not have an average MCV in the low seventies, but in the low eighties.2,3 This explains the most striking feature in the MCV data provided by Reed and Diehl. There is a skew of the gaussian curve of MCV in the low eighties for black men and women, and not for white ones. Thus, their data in blacks are trimodal: the main peak with a mode of about 90 fL; the skew that probably represents 5% to 6% with α2-thalassemia and a mode of about 82 fL;
Bessman D. Congenital Neutropenia: How Low? Arch Intern Med. 1992;152(6):1329. doi:10.1001/archinte.1992.00400180165031
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