Research article
Identifying Adults at High Risk for Diabetes and Cardiovascular Disease Using Hemoglobin A1c: National Health and Nutrition Examination Survey 2005–2006

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Background

The American Diabetes Association (ADA) recently proposed the use of hemoglobin A1c as a practical and valid strategy to identify high-risk people for whom delivery of an intensive lifestyle intervention to prevent type 2 diabetes is likely to be cost effective.

Purpose

To estimate composite risks of developing diabetes and cardiovascular disease (CVD) for adults with different hemoglobin A1c test results and to compare those risks with those of adults who met the 2003 ADA definition for prediabetes.

Methods

Cross-sectional data from the 2005–2006 National Health and Nutrition Examination Survey were analyzed in 2009. The method of Stern and colleagues was used to estimate the 7.5-year probability of type 2 diabetes, and the Framingham General CVD Risk Engine was used to estimate the 10-year probability of CVD for adults with different A1c results. Sample weights were used to account for sampling probability and to adjust for noncoverage and nonresponse.

Results

Among adults meeting the 2003 ADA definition for prediabetes, the probabilities for incident type 2 diabetes (over 7.5 years) and CVD (over 10 years) were 33.5% and 10.7%, respectively. Use of A1c alone, in the range of 5.5% to <6.5%, would identify a population with comparable risks for diabetes (32.4% [SE=1.2%]) and CVD (11.4% [SE=0.6%]). A slightly higher cutoff (≥5.7%) would identify adults with risks of 41.3% (SE=1.5%) for diabetes and 13.3% (SE=0.8%) for CVD—risks that are comparable to people enrolled in the Diabetes Prevention Program.

Conclusions

A1c-based testing in clinical settings should be considered as a means to identify greater numbers of adults at high risk of developing type 2 diabetes and CVD.

Section snippets

Study Design and Sample

The NHANES 2005–2006 surveyed a nationally representative sample of the civilian, noninstitutionalized U.S. population using a stratified, multistage probability sampling design with oversampling of older people and minority groups. Detailed descriptions of the design may be viewed on the National Center for Health Statistics (NCHS) website.21 Among NHANES respondents who were aged ≥18 years, 4751 reported no prior diagnosis of diabetes. Of those who attended the mobile examination center, 2188

Nonselective A1c Testing to Identify Adults at High Risk for Diabetes or Cardiovascular Disease

Among all U.S. adults aged ≥18 years without self-reported diabetes or prior CVD, 30.0% (SE=1.6%) met the 2003 ADA criteria for prediabetes. Within this large group, the mean predicted probabilities for incident diabetes (over 7.5 years) and CVD (over 10 years) were 33.5% (SE=1.0%) and 10.7% (SE=0.8%), respectively. Associations of different A1c test thresholds with predicted risk for diabetes and CVD in adults without self-reported diabetes or prior CVD are shown in Table 1. These data show a

Conclusion

A large majority of people who would meet the 2003 ADA classification for prediabetes are unaware of their risk because of challenges to performing FPG and 2hPG tests routinely.6, 7 A simpler form of high-risk testing could improve diabetes prevention efforts by substantially increasing the numbers of individuals who complete testing. The current study indicates that the A1c test may provide a badly needed, clinically practical indicator of the composite risk for incident diabetes and CVD.

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    Copyright © 2011 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.