Hematocrit levels and race: an argument against the adoption of separate standards in screening for anemia.

The average hematocrit levels of black children have been widely reported to be about two to three percent lower than those of white children. Until recently, the relative contributions of economic, nutritional, and genetic factors to these differences have been unspecified. Based on new evidence and reanalysis of past data, however, some investigators now argue that genetic differences exist which transcend economic status. Separate screening standards are thus recommended for black children-standards which would define fewer as anemic. The present paper discusses methodological inadequacies in the evidence supporting the separate standards argument, focusing on the skewed economic distributions by race which suggest economic disparities within the racial subgroups compared. Findings are presented from a study of children in Washington, DC, to illustrate the role of particular risk factors known to be differentially distributed by income (eg, multiparity, birthweight, source of medical care). These factors are associated with varying hematocrit levels, even among blacks, and they also appear to account for a large part of the black-white hematocrit differentials. Study findings cast doubt on conclusions about the genetic basis of hematocrit differences and suggest that, without better evidence, it would be inappropriate to adopt lower standards for blacks in screening for anemia.