Separate hemoglobin standards for blacks and whites: a critical review of the case for separate and unequal hemoglobin standards.

There have been a number of reports that suggest mean differences between the hemoglobin (Hgb) levels of black and white Americans. Many of those reports have had as their basis various national US nutrition surveys. Early reports indicated that blacks had a 1.0 g/dl lower mean Hgb than whites. Later reports put the mean Hgb difference between 0.5 and 0.73 g/dl. Recent reports, in which either iron intake or iron status have been measured and controlled, indicate a mean Hgb difference of between 0.2 and 0.3 g/dl. Despite the variability in these mean Hgb differences, some reports call for the establishment of separate Hgb standards for black Americans. The need for separate Hgb standards is critically reviewed in light of alternative interpretations of early data and newer knowledge about the development, detection, and significance of iron deficiency. The suitability of national cross-sectional survey data to answer questions about Hgb standards without adequate experimental studies in questioned, especially since no genetic studies have been performed to indicate genetic differences in Hgb levels. Policy implications of a change from current standards are also discussed.