A1C and Diabetes Diagnosis: The Rancho Bernardo Study
- Caroline K. Kramer, MD1,2,
- Maria Rosario G. Araneta, PHD1 and
- Elizabeth Barrett-Connor, MD1
- 1Division of Epidemiology, Department of Family and Preventive Medicine, University of California, San Diego, La Jolla, California;
- 2Division of Endocrinology, Hospital de Clinicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
- Corresponding author: Elizabeth Barrett-Connor, ebarrettconnor{at}ucsd.edu.
Abstract
OBJECTIVE To examine the sensitivity and specificity of A1C as a diagnostic test for type 2 diabetes in older adults.
RESEARCH DESIGN AND METHODS Cross-sectional study of community-dwelling adults without known diabetes who had an oral glucose tolerance test and A1C measured on the same day.
RESULTS Mean age of the 2,107 participants was 69.4 ± 11.1 years; 43% were men. Based on the American Diabetes Association (ADA) criteria, 198 had previously undiagnosed type 2 diabetes. The sensitivity/specificity of A1C cut point of 6.5% was 44/79%. Results were similar in age- and sex-stratified analyses. Given the A1C cut point of 6.5%, 85% of participants were classified as nondiabetic by ADA criteria.
CONCLUSIONS The limited sensitivity of the A1C test may result in delayed diagnosis of type 2 diabetes, while the strict use of ADA criteria may fail to identify a high proportion of individuals with diabetes by A1C ≥6.5% or retinopathy.
Footnotes
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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.
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- Received July 24, 2009.
- Accepted October 6, 2009.
- © 2010 by the American Diabetes Association.
