A1cs are higher in black patients

Levels of hemoglobin A1c are higher in black patients than white, found a new study that could affect methods of screening and monitoring diabetes.

The cross-sectional analysis included 1,581 patients from the Screening for Impaired Glucose Tolerance study and 1,967 from the National Health and Nutrition Examination Survey (NHANES III). A1c levels were compared between black and white patients involved in the trials. The study was published in the June 15 Annals of Internal Medicine.

Black patients had higher average A1c levels, whether they had diabetes, prediabetes or normal glucose tolerance. The difference between the racial groups became greater as glucose intolerance increased; levels were only about 0.2% higher in nondiabetic blacks, but almost 0.5% higher in diabetics. These differences were found even after adjustment for a number of factors, including age, sex, body mass index, education and income. Because none of the patients had previously been diagnosed with diabetes or prediabetes, treatment decisions are unlikely to have confounded the results.

The study confirms previous research that found differences in A1c levels by race, independent of glycemia. The mechanism for the difference is unknown, although study authors speculated on possible physiologic or genetic explanations and recommended that more research be done in this area.

In the meantime, they urged clinicians to recognize the limitations of using A1c to assess glycemic control both in the general population and in individual patients. Greater emphasis on home glucose-monitoring data may be helpful, the authors suggested. Physicians may also want to keep the findings in mind when considering current American Diabetes Association recommendations to diagnose diabetes based on A1c level, noted an accompanying editorial.