David C. Ziemer, MD, MPH; Paul Kolm, PhD; William S. Weintraub, MD; Viola Vaccarino, MD, PhD; Mary K. Rhee, MD, MS; Jennifer G. Twombly, MD, PhD; K.M. Venkat Narayan, MD, MPH, MBA; David D. Koch, PhD; Lawrence S. Phillips, MD
Portions of this work were presented at the 68th Scientific Sessions of the American Diabetes Association, San Francisco, California, 6–10 June 2008.
Acknowledgment: The authors thank Kirsten Herric, MSc, for the NHANES III weighted analyses and Jane Caudle, Circe Tsui, Jack Kaufman, Eileen Osinski, Jade Irving, Rincy Varughese, and Lennisha Pinckney for their assistance.
Grant Support: By the National Institutes of Health and National Center for Research Resources (awards DK07298, DK062668, RR017643, DK066204, and RR00039) and U.S. Department of Veterans Affairs Health Services Research and Development Service (awards SHP 08-144 and IIR 07-138).
Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M09-1619.
Reproducible Research Statement:Study protocol: Not available. Statistical code: Code for weighted analyses available from Dr. Ziemer (e-mail, email@example.com). Data set: Collaborative data sharing available from Dr. Phillips (e-mail, firstname.lastname@example.org).
Corresponding Author: David C. Ziemer, MD, MPH, Division of Endocrinology, Emory University, 49 Jesse Hill Jr. Drive SE, Atlanta, GA 30303.
Current Author Addresses: Drs. Ziemer and Rhee: Division of Endocrinology, Emory University, 49 Jesse Hill Jr. Drive SE, Atlanta, GA 30303.
Drs. Kolm and Weintraub: Christiana Care Health System, 130 Continental Drive, Suite 202, Newark, DE 19713.
Dr. Vaccarino: Emory University School of Medicine, Emory Program in Cardiovascular Outcomes Research and Epidemiology (EPICORE), 1256 Briarcliff Road, Building A, Suite 1 N, Atlanta, GA 30306.
Drs. Twombly and Phillips: Division of Endocrinology, Emory University, 101 Woodruff Circle, Woodruff Memorial Research Building, Room 1027, Atlanta, GA 30322.
Dr. Narayan: School of Public Health, Emory University, 1518-002-7AA (SPH: Global Health), Grace C. Rollins Building 730, Atlanta, GA 30322.
Dr. Koch: Grady Clinical Laboratory, D-119, Grady Health System, 80 Jesse Hill Jr. Drive SE, Atlanta, GA 30303.
Author Contributions: Conception and design: D.C. Ziemer, P. Kolm, K.M.V. Narayan, L.S. Phillips.
Analysis and interpretation of the data: D.C. Ziemer, P. Kolm, W.S. Weintraub, V. Vaccarino, J.G. Twombly, K.M.V. Narayan, D.D. Koch, L.S. Phillips.
Drafting of the article: D.C. Ziemer, J.G. Twombly.
Critical revision of the article for important intellectual content: D.C. Ziemer, P. Kolm, W.S. Weintraub, V. Vaccarino, M.K. Rhee, J.G. Twombly, K.M.V. Narayan, L.S. Phillips.
Final approval of the article: D.C. Ziemer, P. Kolm, W.S. Weintraub, V. Vaccarino, M.K. Rhee, J.G. Twombly, K.M.V. Narayan, D.D. Koch, L.S. Phillips.
Provision of study materials or patients: V. Vaccarino, L.S. Phillips.
Statistical expertise: D.C. Ziemer, P. Kolm, V. Vaccarino.
Obtaining of funding: D.C. Ziemer, W.S. Weintraub, L.S. Phillips.
Administrative, technical, or logistic support: D.C. Ziemer, V. Vaccarino, L.S. Phillips.
Collection and assembly of data: D.C. Ziemer, W.S. Weintraub, D.D. Koch, L.S. Phillips.
Ziemer DC, Kolm P, Weintraub WS, Vaccarino V, Rhee MK, Twombly JG, et al. Glucose-Independent, Black–White Differences in Hemoglobin A1c Levels: A Cross-sectional Analysis of 2 Studies. Ann Intern Med. 2010;152:770-777. doi: 10.7326/0003-4819-152-12-201006150-00004
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Published: Ann Intern Med. 2010;152(12):770-777.
A previous study of participants with prediabetes found that hemoglobin A1c (HbA1c) levels differed between black and white participants with no differences in glucose concentration.
To determine whether blackâ€“white differences in HbA1c level are present in other populations and across the full spectrum of glycemia.
1581 non-Hispanic black and white participants between 18 and 87 years of age without known diabetes in the SIGT (Screening for Impaired Glucose Tolerance) study and 1967 non-Hispanic black and white participants older than 40 years without known diabetes in the NHANES III (Third National Health and Nutrition Examination Survey).
HbA1c levels, anthropometry, and plasma glucose levels during oral glucose tolerance testing.
Hemoglobin A1c levels were higher in black than in white participants with normal glucose tolerance (0.13 percentage point [PÂ < 0.001] in the SIGT sample and 0.21 percentage point [PÂ < 0.001] in the NHANES III sample), prediabetes (0.26 percentage point [PÂ < 0.001] and 0.30 percentage point [PÂ < 0.001], respectively), or diabetes (0.47 percentage point [PÂ < 0.020] and 0.47 percentage point [PÂ < 0.013], respectively) after adjustment for plasma glucose levels and other characteristics known to correlate with HbA1c levels.
The mechanism for the differences is unknown.
Black persons have higher HbA1c levels than white persons across the full spectrum of glycemia, and the differences increase as glucose intolerance worsens. These findings could limit the use of HbA1c to screen for glucose intolerance, indicate the risk for complications, measure quality of care, and evaluate disparities in health.
National Institutes of Health and National Institute of Diabetes, Digestive, and Kidney Diseases.
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Cardiology, Endocrine and Metabolism, Diabetes, Coronary Risk Factors.
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