Are There Clinical Implications of Racial Differences in HbA1c? A Difference, to Be a Difference, Must Make a Difference

Studies that have compared HbA(1c) levels by race have consistently demonstrated higher HbA(1c) levels in African Americans than in whites. These racial differences in HbA(1c) have not been explained by measured differences in glycemia, sociodemographic factors, clinical factors, access to care, or quality of care. Recently, a number of nonglycemic factors and several genetic polymorphisms that operate through nonglycemic mechanisms have been associated with HbA(1c). Their distributions across racial groups and their impact on hemoglobin glycation need to be systematically explored. Thus, on the basis of evidence for racial differences in HbA(1c), current clinical guidelines from the American Diabetes Association state: It is important to take...race/ethnicity...into consideration when using the A1C to diagnose diabetes. However, it is not clear from the guidelines how this recommendation might be actualized. So, the critical question is not whether racial differences in HbA(1c) exist between African Americans and whites; the important question is whether the observed differences in HbA(1c) level are clinically meaningful. Therefore, given the current controversy, we provide a Point-Counterpoint debate on this issue. In the preceding point narrative, Dr. Herman provides his argument that the failure to acknowledge that HbA(1c) might be a biased measure of average glycemia and an unwillingness to rigorously investigate this hypothesis will slow scientific progress and has the potential to do great harm. In the counterpoint narrative below, Dr. Selvin argues that there is no compelling evidence for racial differences in the validity of HbA(1c) as a measure of hyperglycemia and that race is a poor surrogate for differences in underlying causes of disease risk.William T. CefaluEditor in Chief, Diabetes Care