Association of A1C and Fasting Plasma Glucose Levels With Diabetic Retinopathy Prevalence in the U.S. Population

Implications for diabetes diagnostic thresholds

  1. Yiling J. Cheng, MD, PHD1,
  2. Edward W. Gregg, PHD1,
  3. Linda S. Geiss, MA1,
  4. Giuseppina Imperatore, MD, PHD1,
  5. Desmond E. Williams, MD, PHD1,
  6. Xinzhi Zhang, MD, PHD1,
  7. Ann L. Albright, PHD, RD1,
  8. Catherine C. Cowie, PHD2,
  9. Ronald Klein, MD, MPH3 and
  10. Jinan B. Saaddine, MD1
  1. 1Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia;
  2. 2National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland;
  3. 3Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
  1. Corresponding author: Yiling J. Cheng, ycheng{at}cdc.gov.

Abstract

OBJECTIVE To examine the association of A1C levels and fasting plasma glucose (FPG) with diabetic retinopathy in the U.S. population and to compare the ability of the two glycemic measures to discriminate between people with and without retinopathy.

RESEARCH DESIGN AND METHODS This study included 1,066 individuals aged ≥40 years from the 2005–2006 National Health and Nutrition Examination Survey. A1C, FPG, and 45° color digital retinal images were assessed. Retinopathy was defined as a level ≥14 on the Early Treatment Diabetic Retinopathy Study severity scale. We used joinpoint regression to identify linear inflections of prevalence of retinopathy in the association between A1C and FPG.

RESULTS The overall prevalence of retinopathy was 11%, which is appreciably lower than the prevalence in people with diagnosed diabetes (36%). There was a sharp increase in retinopathy prevalence in those with A1C ≥5.5% or FPG ≥5.8 mmol/l. After excluding 144 people using hypoglycemic medication, the change points for the greatest increase in retinopathy prevalence were A1C 5.5% and FPG 7.0 mmol/l. The coefficients of variation were 15.6 for A1C and 28.8 for FPG. Based on the areas under the receiver operating characteristic curves, A1C was a stronger discriminator of retinopathy (0.71 [95% CI 0.66–0.76]) than FPG (0.65 [0.60 – 0.70], P for difference = 0.009).

CONCLUSIONS The steepest increase in retinopathy prevalence occurs among individuals with A1C ≥5.5% and FPG ≥5.8 mmol/l. A1C discriminates prevalence of retinopathy better than FPG.

Footnotes

  • The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention, the National Institute of Diabetes and Digestive and Kidney Diseases, or the University of Wisconsin School of Medicine and Public Health.

  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

  • See accompanying editorial, p. 2140.

    • Received March 6, 2009.
    • Accepted June 13, 2009.
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