Improvements needed in the clinical use of HbA1c for diagnosing and managing diabetes across race/ethnicities

Research from Rollins School of Public Health suggests that blacks have higher levels of HbA1c than whites at the same glucose levels, leading to a possible overdiagnosis of diabetes in blacks. The study was recently published in the journal Diabetic Medicine.

HbA1c, sometimes referred to as hemoglobin A1C or simply A1c, is a glycated protein that physicians look at to determine average blood sugar levels over a period of time. 

Christopher Ford, postdoctoral fellow at Rollins, is first author of the study. Lisa R. Staimez, PhD, assistant professor at Rollins, is senior author of the study. Her research focuses on the prevention of chronic diseases globally and the risk factors of diabetes development. 

Using Youden’s index, a measure which incorporates both sensitivity and specificity, the researchers found that optimal HbA1c cutoffs were 2 mmol/mol (0.2%) to 5 mmol/mol (0.5%) higher for blacks than for whites compared to underlying glucose levels as measured by oral glucose tolerance tests. Therefore, current HbA1c diagnostic criteria may over diagnose diabetes or prediabetes in more black than white patients.

“Differences in HbA1c suggest a need to individualize HbA1c interpretation for diagnosis and treatment of diabetes and prediabetes,” the authors note. 

Other authors on the paper included: Whitney Leet and Lauren Kipling from Rollins; Sandra Jackson from the Centers for Disease Control and Prevention; and Lawrence Phillips, MD, professor of endocrinology; Peter W. Wilson, professor of cardiology; and Mary Rhee, associate professor of endocrinology, from the Emory University School of Medicine and the Atlanta VA Medical Center.