• Richard M Bergenstal, Robin L Gal, Crystal G Connor, Rose Gubitosi-Klug, Davida Kruger, Beth A Olson, Steven M Willi, Grazia Aleppo, Ruth S Weinstock, Jamie Wood, Michael Rickels, Linda A DiMeglio, Kathleen E Bethin, Santica Marcovina, Andreana Tassopoulos, Sooji Lee, Elaine Massaro, Suzan Bzdick, Brian Ichihara, Eileen Markmann, Paul McGuigan, Stephanie Woerner, Michelle Ecker, Roy W Beck, and T1D Exchange Racial Differences Study Group.
• From International Diabetes Center Park Nicollet, Minneapolis, Minnesota; Jaeb Center for Health Research, Tampa, Florida; University Hospitals of Cleveland, Cleveland, Ohio; Henry Ford Health System, Detroit, Michigan; Children's Hospital of Philadelphia and Perelman School of Medicine and Rodebaugh Diabetes Center, University of Pennsylvania, Philadelphia, Pennsylvania; Northwestern University, Chicago, Illinois; SUNY Upstate Medical University, Syracuse, New York; Children's Hospital of Los Angeles, Los Angeles, California; Indiana University School of Medicine, Indianapolis, Indiana; SUNY Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York; and Northwest Lipid Metabolism and Diabetes Research Laboratories, Seattle, Washington.
• Ann. Intern. Med. 2017 Jul 18; 167 (2): 9510295-102.

BackgroundDebate exists as to whether the higher hemoglobin A1c (HbA1c) levels observed in black persons than in white persons are due to worse glycemic control or racial differences in the glycation of hemoglobin.ObjectiveTo determine whether a racial difference exists in the relationship of mean glucose and HbA1c.DesignProspective, 12-week observational study.Setting10 diabetes centers in the United States.Participants104 black persons and 104 white persons aged 8 years or older who had had type 1 diabetes for at least 2 years and had an HbA1c level of 6.0% to 12.0%.MeasurementsMean glucose concentration, measured by using continuous glucose monitoring and compared by race with HbA1c, glycated albumin, and fructosamine values.ResultsThe mean HbA1c level was 9.1% in black persons and 8.3% in white persons. For a given HbA1c level, the mean glucose concentration was significantly lower in black persons than in white persons (P = 0.013), which was reflected in mean HbA1c values in black persons being 0.4 percentage points (95% CI, 0.2 to 0.6 percentage points) higher than those in white persons for a given mean glucose concentration. In contrast, no significant racial differences were found in the relationship of glycated albumin and fructosamine levels with the mean glucose concentration (P > 0.20 for both comparisons).LimitationThere were too few participants with HbA1c levels less than 6.5% to generalize the results to such individuals.ConclusionOn average, HbA1c levels overestimate the mean glucose concentration in black persons compared with white persons, possibly owing to racial differences in the glycation of hemoglobin. However, because race only partially explains the observed HbA1c differences between black persons and white persons, future research should focus on identifying and modifying barriers impeding improved glycemic control in black persons with diabetes.Primary Funding SourceHelmsley Charitable Trust.

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