Hemoglobin difference between black and white women with comparable iron status: justification for race-specific anemia criteria.

To determine the appropriateness of race-specific criteria for anemia, we used the sample of women of child-bearing age from the Second National Health and Examination Survey to examine the relationship between hemoglobin and iron status for blacks and whites. After adjustment for major factors known to cause hemoglobin variation, including iron nutrition status, black women overall had a significantly lower mean hemoglobin value (126 +/- 12 g/L) than white women (134 +/- 11 g/L). Comparison of the probability plots of black and white hemoglobin distributions found the difference across the distributions to not be uniform, likely because a subset of black women had lower hemoglobin values rather than because of a generalized lowering. This finding suggests that it may not be appropriate to have a separate criteria for all blacks to accommodate the subset with lower hemoglobin. However, evaluation of the screening performance of hemoglobin found that race-specific anemia criteria (10 g/L difference) yielded a comparable sensitivity and specificity in detecting iron deficiency for both races. In contrast, a fixed anemia criterion did not yield comparable screening performances for the two races. This functional evaluation supports considering race-specific anemia criteria for screening iron deficiency.