Diabetes is a common ailment within the United States, affecting approximately 8% of the population. Current guidelines recommend using a glycated hemoglobin (HbA_1c) level of 6.5% or higher as the diagnostic cutoff for diabetes; however, there's debate over whether that cutoff should vary according to race-in particular, whether it should be higher for black adults than white adults-because research shows consistently higher HbA_1c levels in blacks at all blood glucose levels. The authors of a recent study analyzed the relationship between HbA_1c level and retinopathy, another determinant of diabetes, in white and black Americans ages 40 years and older.

The cross-sectional study looked at data from 2,804 white and 1,008 black respondents in the National Health and Nutrition Examination Survey from 2005 through 2008. As expected, baseline HbA_1c levels were higher in the black respondents. After adjustment for variables such as age, sex, hypertension, and body mass index, the risk of diabetic retinopathy in black people with an HbA_1c level of 5.5% to 5.9% was similar to that among white people with an HbA_1c level of 6% to 6.4%. These findings were consistent after excluding patients being treated for diabetes from the analysis. The data also show that black adults are at greater risk for developing retinopathy than white adults at an HbA_1c level between 5% and 7%.

The results indicate that although black people tend to have higher HbA_1c levels than white people-regardless of glycemic level-retinopathy resulting from diabetes occurs at lower HbA_1c levels in black than in white people.

Although the authors point out a number of study limitations, including the inability to monitor HbA_1c levels over time, and call for long-term longitudinal studies with larger sample sizes, they conclude that the results of their study do not support increasing the HbA_1c level considered to be diagnostic of diabetes in black patients.

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