Relationship Between Average Glucose Levels and HbA1c Differs Across Racial Groups: A Substudy of the GRADE Randomized Trial

David M. Nathan, Diabetes Clinical Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
William H. Herman, Departments of Internal Medicine and Epidemiology, University of Michigan, Ann Arbor, MI.
Mary E. Larkin, Diabetes Clinical Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Heidi Krause-Steinrauf, Biostatistics Center, Department of Biostatistics and Bioinformatics, Milken Institute School of Public Health, George Washington University, Rockville, MD.
Hiba Abou Assi, Duke University Medical Center, Durham, NC.
Andrew J. Ahmann, Oregon Health & Science University, Portland, OR.
Janet Brown-Friday, Department of Medicine (Endocrinology), Albert Einstein College of Medicine, Bronx, NY.
Daniel S. Hsia, Pennington Biomedical Research Center, Baton Rouge, LA.
Tasma Harindhanavudhi, University of Minnesota, Minneapolis, MN.
Mary Johnson, International Diabetes Center, Health Partners Institute, Minneapolis, MN.
Valerie L. Arends, Advanced Research and Diagnostic Laboratory, Department of Laboratory Medicine, University of Minnesota, Minneapolis, MN.
Nicole M. Butera, Biostatistics Center, Department of Biostatistics and Bioinformatics, Milken Institute School of Public Health, George Washington University, Rockville, MD.
Samuel P. Rosin, Biostatistics Center, Department of Biostatistics and Bioinformatics, Milken Institute School of Public Health, George Washington University, Rockville, MD.
John M. Lachin, Biostatistics Center, Department of Biostatistics and Bioinformatics, Milken Institute School of Public Health, George Washington University, Rockville, MD.
Naji Younes, Biostatistics Center, Department of Biostatistics and Bioinformatics, Milken Institute School of Public Health, George Washington University, Rockville, MD.

Document Type

Journal Article

Publication Date

9-23-2024

Journal

Diabetes care

DOI

10.2337/dc24-1362

Abstract

OBJECTIVE: To determine whether the relationship between average glucose (AG) levels and hemoglobin A1c (HbA1c) differs across racial/ethnic groups. RESEARCH DESIGN AND METHODS: We performed a prospective substudy of GRADE, a comparative effectiveness randomized trial conducted in 36 centers in the U.S. A total of 1,454 of the 5,047 participants in the GRADE cohort, including 534 non-Hispanic White (NHW), 389 non-Hispanic Black (NHB), and 327 Hispanic White patients and 204 patients of other racial/ethnic backgrounds, were included in the substudy. Continuous glucose monitoring (CGM) performed for 10 days was used to calculate AG10. Immediately after CGM, HbA1c and glycated albumin were measured. Fasting plasma glucose (FPG) and glucose area under the curve (AUC) were derived from a 75-g oral glucose tolerance test. RESULTS: The relationship between AG10 and HbA1c was significantly different for NHB compared with NHW patients and those of other racial/ethnic groups. HbA1c levels were 0.2-0.6 percentage points higher in NHB than in NHW patients for AG10 levels from 100 to 250 mg/dL. For an HbA1c of 7%, AG10 was 11 mg/dL higher for NHW than for NHB patients. Similar findings were observed across races for relationships of FPG and AUC with HbA1c and for glucose measurements with glycated albumin levels. Differences in the relationship between AG10 and HbA1c across racial groups remained after adjustments for any demographic or other differences between racial/ethnic subgroups. CONCLUSIONS: The relationship between several measures of glucose with HbA1c and glycated albumin consistently differed across races. These findings should be considered in setting treatment goals and diagnostic levels.

Department

Biostatistics and Bioinformatics

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