Are there clinical implications of racial differences in HbA_1c? 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 unwillingnessto 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.