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Racial and Ethnic Differences in Mean Plasma Glucose, Hemoglobin A_1c, and 1,5-Anhydroglucitol in Over 2000 Patients with Type 2 Diabetes

Internal Medicine and Epidemiology (W.H.H.), University of Michigan, Ann Arbor, Michigan 48109; Ohio State University (K.M.D.), Columbus, Ohio 43210; Department of Endocrinology and Metabolism (B.H.R.W.), University Medical Center Groningen, and University of Groningen, 9700 RB Groningen, The Netherlands; Division of Endocrinology (J.B.B.), University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599; and U.S. Medical Division (J.L.F., H.J., S.M.), Lilly USA, LLC, Indianapolis, Indiana 46285

Address all correspondence and requests for reprints to: William H. Herman, M.D., M.P.H., University of Michigan Health System, 1500 E. Medical Center Drive, 3920 Taubman Center, SPC 5354, Ann Arbor, Michigan 48109. E-mail: wherman{at}umich.edu.

Content: Recent studies have reported hemoglobin A_1c (A1c) differences across racial/ethnic groups. Our diverse population allows for further investigation of potential differences in measurements of glycemia.

Objectives: Our objectives were to describe and explore baseline racial/ethnic differences in self-monitored plasma glucose profiles, A1c, and 1,5-anhydroglucitol (1,5-AG) in patients with type 2 diabetes enrolled in the Assessing DURAbility of Basal vs. Lispro Mix 75/25 Insulin Efficacy trial.

Design, Setting, Patients: The trial enrolled 2094 patients with type 2 diabetes, ages 30–80 yr, from 11 countries.

Main Outcome Measures: Estimated mean plasma glucose (MPG), A1c, and 1,5-AG were compared among racial/ethnic groups before and after adjusting for factors affecting glycemia: age, sex, duration of diabetes, body mass index, and MPG.

Results: Baseline estimated MPG ± SD was 220.0 ± 82.0 mg/dl, mean A1c was 9.0 ± 1.3%, and 1,5-AG was 5.0 ± 4.1µg/ml. Estimated MPG did not differ between Caucasian and non-Caucasian groups. A1c was higher in Hispanics (9.4 ± 1.4%; P < 0.001), Asians (9.2 ± 1.4%; P < 0.01), and patients of other racial/ethnic groups (9.7 ± 1.5%; P < 0.001) compared with Caucasians (8.9 ± 1.2%). Paradoxically, 1,5-AG was higher for Asian (5.7 ± 4.6 µg/ml) and African patients (6.2 ± 5.4 µg/ml) vs. Caucasians (4.9 ± 3.9 µg/ml) (P < 0.01). After adjusting for factors affecting glycemia, A1c was higher (all P 0.002) in Hispanics, Asians, Africans, and patients of other racial/ethnic groups, and 1,5-AG was higher in Asian and African patients (P < 0.001) vs. Caucasians.

Conclusions: There were differences in A1c and 1,5-AG, but not MPG, among racial/ethnic groups. Comparisons of glycemia across racial/ethnic groups using these parameters may be problematic due to inherent biological variability and methodological issues.