Yusuke Tsugawa, MD, MPH; Kenneth J. Mukamal, MD, MPH; Roger B. Davis, ScD; William C. Taylor, MD; Christina C. Wee, MD, MPH
Disclaimer: Dr. Tsugawa had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Acknowledgment: The authors thank the National Center for Health Statistics for providing the data and Ms. Karen Huskey (Beth Israel Deaconess Medical Center) for her assistance with some of the statistical analyses.
Financial Support: Dr. Tsugawa is supported by the Shigeaki Hinohara, MD, Primary Care Fellowship at Beth Israel Deaconess Medical Center; the Joint Japan/World Bank Graduate Scholarship Program; and St. Luke's Life Science Institute, Tokyo, Japan. Dr. Davis is supported by Harvard Catalyst, The Harvard Clinical and Translational Science Center (National Institutes of Health Award UL1 RR 025758), and financial contributions from Harvard University and its affiliated academic health care centers. Dr. Wee is supported by a midcareer mentorship award from the National Institutes of Health (K24DK087932).
Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M11-2083.
Reproducible Research Statement:Study protocol: Not available. Statistical code: Available from Dr. Tsugawa (e-mail, email@example.com). Data set: Available from the National Center for Health Statistics (www.cdc.gov/nchs/nhanes.htm).
Requests for Single Reprints: Yusuke Tsugawa, MD, MPH, Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center, Harvard Medical School, 1309 Beacon Street, Brookline, MA 02446; e-mail, firstname.lastname@example.org.
Current Author Addresses: Drs. Tsugawa, Mukamal, Davis, Taylor, and Wee: Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215.
Author Contributions: Conception and design: Y. Tsugawa, C.C. Wee, K.J. Mukamal, W.C. Taylor.
Analysis and interpretation of the data: Y. Tsugawa, K.J. Mukamal, R.B. Davis, C.C. Wee.
Drafting of the article: Y. Tsugawa, C.C. Wee.
Critical revision of the article for important intellectual content: Y. Tsugawa, K.J. Mukamal, R.B. Davis, W.C. Taylor, C.C. Wee.
Final approval of the article: Y. Tsugawa, K.J. Mukamal, R.B. Davis, W.C. Taylor, C.C. Wee.
Statistical expertise: R.B. Davis.
Administrative, technical, or logistic support: Y. Tsugawa.
Collection and assembly of data: Y. Tsugawa.
Hemoglobin A1c (HbA1c) levels are known to be consistently higher in black persons than in white persons at any given glycemic level. Whether the optimal diagnostic threshold of HbA1c should differ between blacks and whites is unclear.
To compare the relationships between HbA1c level and the prevalence of retinopathy in black and white U.S. adults.
A nationally representative sample of the National Health and Nutrition Examination Survey from 2005 through 2008.
2804 white persons and 1008 black persons aged 40 years or older in the United States.
Prevalence of retinopathy. Logistic regression models and restricted cubic spline models were constructed separately for white and black populations to test the HbA1c levels at which risk for retinopathy begins to increase.
After adjustment for age, sex, hypertension, body mass index, family history of diabetes, and use of antidiabetes medications or insulin, the lowest HbA1c category for which the prevalence of retinopathy was significantly higher than the reference category (<5.5%) was 6.0% to 6.4% for white persons (risk difference, 4.8% [95% CI, 0.5% to 9.1%]) and 5.5% to 5.9% for black persons (risk difference, 5.3% [CI, 1.0% to 9.5%]). The restricted cubic spline models indicated that the risk for retinopathy increased at lower HbA1c levels in black persons than in white persons.
The cross-sectional design of the study precluded examining the effect of the duration at each HbA1c level.
The prevalence of retinopathy begins to increase at a lower HbA1c level in black Americans than in white Americans. The findings do not support increasing the diagnostic threshold of HbA1c in black persons.
Tsugawa Y, Mukamal KJ, Davis RB, et al. Should the Hemoglobin A1c Diagnostic Cutoff Differ Between Blacks and Whites?: A Cross-sectional Study. Ann Intern Med. 2012;157:153–159. doi: 10.7326/0003-4819-157-3-201208070-00004
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Published: Ann Intern Med. 2012;157(3):153-159.
Cardiology, Coronary Risk Factors, Diabetes, Endocrine and Metabolism.
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