The blood hemoglobin concentration, MCV, TS, and serum ferritin of 598 African-American men and women and more than 12 000 age-matched white controls attending a Health Appraisal Clinic. The African-American subjects profiled in the figure were attending a Health Appraisal Clinic and were genotyped for α-thalassemia and hemoglobin S. The error bars represent one standard error of the mean. (A) All subjects without exclusions. (B) Subjects after removing those with iron deficiency (see “Patients, materials, and methods”). AA indicates African-American. Error bars indicate standard error of the mean (SEM).