Skip to main content
  • More from ADA
    • Diabetes
    • Clinical Diabetes
    • Diabetes Spectrum
    • ADA Standards of Medical Care
    • ADA Scientific Sessions Abstracts
    • BMJ Open Diabetes Research & Care
  • Subscribe
  • Log in
  • My Cart
  • Follow ada on Twitter
  • RSS
  • Visit ada on Facebook
Diabetes Care

Advanced Search

Main menu

  • Home
  • Current
    • Current Issue
    • Online Ahead of Print
    • Special Article Collections
    • ADA Standards of Medical Care
  • Browse
    • By Topic
    • Issue Archive
    • Saved Searches
    • Special Article Collections
    • ADA Standards of Medical Care
  • Info
    • About the Journal
    • About the Editors
    • ADA Journal Policies
    • Instructions for Authors
    • Guidance for Reviewers
  • Reprints/Reuse
  • Advertising
  • Subscriptions
    • Individual Subscriptions
    • Institutional Subscriptions and Site Licenses
    • Access Institutional Usage Reports
    • Purchase Single Issues
  • Alerts
    • E­mail Alerts
    • RSS Feeds
  • Podcasts
    • Diabetes Core Update
    • Special Podcast Series: Therapeutic Inertia
    • Special Podcast Series: Influenza Podcasts
    • Special Podcast Series: SGLT2 Inhibitors
    • Special Podcast Series: COVID-19
  • Submit
    • Submit a Manuscript
    • Journal Policies
    • Instructions for Authors
    • ADA Peer Review
  • More from ADA
    • Diabetes
    • Clinical Diabetes
    • Diabetes Spectrum
    • ADA Standards of Medical Care
    • ADA Scientific Sessions Abstracts
    • BMJ Open Diabetes Research & Care

User menu

  • Subscribe
  • Log in
  • My Cart

Search

  • Advanced search
Diabetes Care
  • Home
  • Current
    • Current Issue
    • Online Ahead of Print
    • Special Article Collections
    • ADA Standards of Medical Care
  • Browse
    • By Topic
    • Issue Archive
    • Saved Searches
    • Special Article Collections
    • ADA Standards of Medical Care
  • Info
    • About the Journal
    • About the Editors
    • ADA Journal Policies
    • Instructions for Authors
    • Guidance for Reviewers
  • Reprints/Reuse
  • Advertising
  • Subscriptions
    • Individual Subscriptions
    • Institutional Subscriptions and Site Licenses
    • Access Institutional Usage Reports
    • Purchase Single Issues
  • Alerts
    • E­mail Alerts
    • RSS Feeds
  • Podcasts
    • Diabetes Core Update
    • Special Podcast Series: Therapeutic Inertia
    • Special Podcast Series: Influenza Podcasts
    • Special Podcast Series: SGLT2 Inhibitors
    • Special Podcast Series: COVID-19
  • Submit
    • Submit a Manuscript
    • Journal Policies
    • Instructions for Authors
    • ADA Peer Review
Original Research

Comparison of A1C and Fasting Glucose Criteria to Diagnose Diabetes Among U.S. Adults

  1. April P. Carson, PHD1,
  2. Kristi Reynolds, PHD2,
  3. Vivian A. Fonseca, MD3 and
  4. Paul Muntner, PHD1
  1. 1Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama;
  2. 2Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California;
  3. 3Scott and White Clinic, Texas A&M Health Sciences Center, Temple, Texas.
  1. Corresponding author: April P. Carson, apcarson{at}uab.edu.
Diabetes Care 2010 Jan; 33(1): 95-97. https://doi.org/10.2337/dc09-1227
PreviousNext
  • Article
  • Figures & Tables
  • Suppl Material
  • Info & Metrics
  • PDF
Loading

Abstract

OBJECTIVE To compare A1C and fasting glucose for the diagnosis of diabetes among U.S. adults.

RESEARCH DESIGN AND METHODS This study included 6,890 adults (≥20 years of age) from the 1999–2006 National Health and Nutrition Examination Survey without a self-reported history of diabetes who had fasted ≥9 h. A1C ≥6.5% and fasting glucose ≥126 mg/dl were used, separately, to define diabetes.

RESULTS Overall, 1.8% of U.S. adults had A1C ≥6.5% and fasting glucose ≥126 mg/dl, 0.5% had A1C ≥6.5% and fasting glucose <126 mg/dl, and 1.8% had A1C <6.5% and fasting glucose ≥126 mg/dl. Compared with individuals with A1C <6.5% and fasting glucose ≥126 mg/dl, individuals with A1C ≥6.5% and fasting glucose <126 mg/dl were younger, more likely to be non-Hispanic black, had lower Hb levels, and had higher C-reactive protein.

CONCLUSIONS A1C ≥6.5% demonstrates reasonable agreement with fasting glucose for diagnosing diabetes among U.S. adults.

In June 2009, the International Expert Committee released a report that recommended the use of A1C to diagnose diabetes (1). Previously, A1C had been used primarily to monitor glycemic control among individuals with diabetes. However, over the last decade, the A1C measurement has become standardized (2,3), facilitating its recognition as an acceptable diagnostic method for diabetes.

Before the release of this report, diabetes was mainly defined using a fasting plasma glucose ≥126 mg/dl (≥7.0 mmol/l) in the U.S (4). Using A1C (≥6.5%) to diagnose diabetes may identify different individuals than fasting plasma glucose because the two methods assess different elements of glucose metabolism (1). The purpose of this study was to compare A1C ≥6.5% and fasting plasma glucose ≥126 mg/dl for the identification of undiagnosed diabetes among participants in the U.S. National Health and Nutrition Examination Survey (NHANES). Additionally, we calculated the demographic characteristics and cardiovascular risk profile for individuals diagnosed with diabetes by each of these methods.

RESEARCH DESIGN AND METHODS

NHANES 1999–2000, 2001–2002, 2003–2004, and 2005–2006 are serial cross-sectional surveys including nationally representative samples of the noninstitutionalized civilian U.S. population identified through a stratified, multistage probability sampling design. Methods for pooling these datasets have been published (5). The current analysis was limited to 6,890 participants without self-reported diabetes who attended a morning examination, fasted for ≥9 h at the time of their blood collection, and had valid plasma glucose and A1C values.

Data were collected through questionnaires (demographics, medical history), a physical examination (blood pressure), and blood collection (lipids, plasma glucose, A1C). Plasma glucose was measured using a modified hexokinase enzymatic method and A1C using high-performance liquid chromatography. The coefficient of variation was <3% in each 2-year period for glucose and <2% for A1C.

Participants were categorized into one of four mutually exclusive groups by the presence or absence of fasting plasma glucose ≥126 mg/dl and A1C ≥6.5%. The distribution of the population into these groupings was determined. The κ statistic was calculated as a measure of agreement. Characteristics of the study population were calculated for each group with the statistical significance of differences determined using least squares and maximum likelihood estimation for continuous and categorical variables, respectively. In secondary analyses, the distribution of U.S. adults by fasting glucose and different A1C cut-points (6.0–6.7%) were calculated. Also, sensitivity, specificity, positive and negative predictive values, and number of U.S. adults misclassified were calculated using different A1C cut-points. Analyses were weighted to represent the U.S. population and conducted using SUDAAN (version 9; Research Triangle Institute) to account for the complex survey design.

RESULTS

Among U.S. adults, the prevalence of undiagnosed diabetes was 2.3% using A1C and 3.6% using fasting glucose. Moderate agreement existed for A1C and fasting glucose diagnoses (κ = 0.60; 95% CI 0.55–0.64). Diabetes classification was consistent for the majority of the study participants, with 95.9% classified as not having diabetes by both A1C and fasting glucose and 1.8% classified as having diabetes by both A1C and fasting glucose (Table 1). Discordant classifications occurred for 0.5% of participants who had an A1C ≥6.5% and fasting glucose <126 mg/dl and for 1.8% who had an A1C <6.5% and fasting glucose ≥126 mg/dl. Among individuals with an A1C ≥6.5% and fasting glucose <126 mg/dl, 82% had impaired fasting glucose (100–125 mg/dl). Among individuals with an A1C <6.5% and a fasting glucose ≥126 mg/dl, 45% had an A1C value ≥6.0% but <6.5% (i.e., elevated risk for diabetes using the new A1C guidelines).

View this table:
  • View inline
  • View popup
Table 1

Characteristics of NHANES participants (1999–2006) without self-reported diabetes, by A1C and fasting plasma glucose

The demographic and cardiovascular profile differed for participants with A1C ≥6.5% and fasting glucose <126 mg/dl compared with individuals with A1C <6.5% and fasting glucose ≥126 mg/dl. Specifically, participants with A1C ≥6.5% and fasting glucose <126 mg/dl were younger, more likely to be non-Hispanic black, had lower Hb, and higher C-reactive protein values.

The distribution of adults by fasting glucose and different A1C cut points are available in Table S1 (which is located in an online-only appendix at http://care.diabetesjournals.org/cgi/content/full/dc09-1227/DC1). Overall, lower A1C cut points resulted in higher sensitivity and lower specificity (Table S2).

CONCLUSIONS

The results of the current study indicate the new recommendation by the International Expert Committee to use A1C to diagnose diabetes would result in the same classification as fasting glucose for 97.7% of U.S. adults. For those with discordant results, 0.5% of U.S. adults had A1C ≥6.5% and fasting glucose <126 mg/dl, whereas 1.8% had A1C <6.5% and fasting glucose ≥126 mg/dl. Discordance in the diagnosis of diabetes using A1C and fasting glucose was expected and is likely due to the assessment of different aspects of glucose metabolism (1). For example, participants with an A1C ≥6.5% and fasting glucose <126 mg/dl may have been diagnosed by an oral glucose tolerance test, which was not available for the majority of participants in this study.

About 1.8% of U.S. adults had A1C <6.5% and fasting glucose ≥126 mg/dl and would not be classified as having diabetes using the new recommendation. However, as defined using the report's guidelines, almost half of these individuals would be identified as high risk for diabetes based on A1C values between 6.0 and 6.4%. Although these adults would not satisfy the new A1C recommendation for the diagnosis of diabetes, they would be targeted for preventive therapy to reduce diabetes risk, which may also prompt a fasting glucose measurement. Using a lower A1C cut point would result in more diabetes diagnoses among this group; however, there would also be a tradeoff with substantially more diabetes diagnoses among individuals who would have previously been classified as not having diabetes using fasting glucose alone.

Subgroup differences were noted in this study, with a higher percentage of individuals diagnosed with diabetes via A1C versus with fasting glucose being non-Hispanic black and of younger age. These differences are similar to previous reports (6–8), but caution should be used when comparing estimates across subgroups because of the limited sample size in this study.

In summary, A1C may be an appropriate method for diagnosing diabetes, although clinical implications for using different A1C cut points warrant further investigation.

Acknowledgments

No potential conflicts of interest relevant to this article were reported.

Footnotes

  • 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.

    • Received July 6, 2009.
    • Accepted September 21, 2009.
  • Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

  • © 2010 by the American Diabetes Association.

References

  1. ↵
    International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care 2009; 32: 1327– 1334
    OpenUrlFREE Full Text
  2. ↵
    Consensus Committee. Consensus statement on the worldwide standardization of the hemoglobin A1C measurement: the American Diabetes Association, European Association for the Study of Diabetes, International Federation of Clinical Chemistry and Laboratory Medicine, and the International Diabetes Federation. Diabetes Care 2007; 30: 2399– 2400
    OpenUrlFREE Full Text
  3. ↵
    1. Little RR
    : Glycated hemoglobin standardization: National Glycohemoglobin Standardization Program (NGSP) perspective. Clin Chem Lab Med 2003; 41: 1191– 1198
    OpenUrlCrossRefPubMedWeb of Science
  4. ↵
    Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 2003; 26( Suppl. 1): S5– S20
    OpenUrlCrossRefPubMedWeb of Science
  5. ↵
    Centers for Disease Control and Prevention (CDC). National Center for Health Statistics (NCHS). Analytic and Reporting Guidelines: The National Health and Nutrition Examination Survey (NHANES). Available at http://www.cdc.gov/nchs/data/nhanes/nhanes_03_04/nhanes_analytic_guidelines_dec_2005.pdf. Accessed 30 June 2009
  6. ↵
    1. Ford ES,
    2. Li C,
    3. Little RR,
    4. Mokdad AH
    : Trends in A1C concentrations among U.S. adults with diagnosed diabetes from 1999 to 2004. Diabetes Care 2008; 31: 102– 104
    OpenUrlFREE Full Text
  7. ↵
    1. Herman WH,
    2. Ma Y,
    3. Uwaifo G,
    4. Haffner S,
    5. Kahn SE,
    6. Horton ES,
    7. Lachin JM,
    8. Montez MG,
    9. Brenneman T,
    10. Barrett-Connor E
    : the Diabetes Prevention Program Research Group. Differences in A1C by race and ethnicity among patients with impaired glucose tolerance in the Diabetes Prevention Program. Diabetes Care 2007; 30: 2453– 2457
    OpenUrlAbstract/FREE Full Text
  8. ↵
    1. Selvin E,
    2. Zhu H,
    3. Brancati FL
    : Elevated A1C in adults without a history of diabetes in the U.S. Diabetes Care 2009; 32: 828– 833
    OpenUrlAbstract/FREE Full Text
PreviousNext
Back to top
Diabetes Care: 33 (1)

In this Issue

January 2010, 33(1)
  • Table of Contents
  • About the Cover
  • Index by Author
Sign up to receive current issue alerts
View Selected Citations (0)
Print
Download PDF
Article Alerts
Sign In to Email Alerts with your Email Address
Email Article

Thank you for your interest in spreading the word about Diabetes Care.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
Comparison of A1C and Fasting Glucose Criteria to Diagnose Diabetes Among U.S. Adults
(Your Name) has forwarded a page to you from Diabetes Care
(Your Name) thought you would like to see this page from the Diabetes Care web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
Comparison of A1C and Fasting Glucose Criteria to Diagnose Diabetes Among U.S. Adults
April P. Carson, Kristi Reynolds, Vivian A. Fonseca, Paul Muntner
Diabetes Care Jan 2010, 33 (1) 95-97; DOI: 10.2337/dc09-1227

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Add to Selected Citations
Share

Comparison of A1C and Fasting Glucose Criteria to Diagnose Diabetes Among U.S. Adults
April P. Carson, Kristi Reynolds, Vivian A. Fonseca, Paul Muntner
Diabetes Care Jan 2010, 33 (1) 95-97; DOI: 10.2337/dc09-1227
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Google Plus One

Jump to section

  • Article
    • Abstract
    • RESEARCH DESIGN AND METHODS
    • RESULTS
    • CONCLUSIONS
    • Acknowledgments
    • Footnotes
    • References
  • Figures & Tables
  • Suppl Material
  • Info & Metrics
  • PDF

Related Articles

Cited By...

More in this TOC Section

Original Research

  • The SimpliciT1 Study: A Randomized, Double-Blind, Placebo-Controlled Phase 1b/2 Adaptive Study of TTP399, a Hepatoselective Glucokinase Activator, for Adjunctive Treatment of Type 1 Diabetes
  • Newborn Adiposity and Cord Blood C-Peptide as Mediators of the Maternal Metabolic Environment and Childhood Adiposity
  • Cost-effectiveness of Community-Based Depression Interventions for Rural and Urban Adults With Type 2 Diabetes: Projections From Program ACTIVE (Adults Coming Together to Increase Vital Exercise) II
Show more Original Research

Epidemiology/Health Services Research

  • Trajectories of Childhood Adversity and Type 1 Diabetes: A Nationwide Study of One Million Children
  • Risk of Blindness Among Patients With Diabetes and Newly Diagnosed Diabetic Retinopathy
  • Prediabetes, Diabetes, and the Risk of All-Cause and Cause-Specific Mortality in a Japanese Working Population: Japan Epidemiology Collaboration on Occupational Health Study
Show more Epidemiology/Health Services Research

Similar Articles

Navigate

  • Current Issue
  • Standards of Care Guidelines
  • Online Ahead of Print
  • Archives
  • Submit
  • Subscribe
  • Email Alerts
  • RSS Feeds

More Information

  • About the Journal
  • Instructions for Authors
  • Journal Policies
  • Reprints and Permissions
  • Advertising
  • Privacy Policy: ADA Journals
  • Copyright Notice/Public Access Policy
  • Contact Us

Other ADA Resources

  • Diabetes
  • Clinical Diabetes
  • Diabetes Spectrum
  • Scientific Sessions Abstracts
  • Standards of Medical Care in Diabetes
  • BMJ Open - Diabetes Research & Care
  • Professional Books
  • Diabetes Forecast

 

  • DiabetesJournals.org
  • Diabetes Core Update
  • ADA's DiabetesPro
  • ADA Member Directory
  • Diabetes.org

© 2021 by the American Diabetes Association. Diabetes Care Print ISSN: 0149-5992, Online ISSN: 1935-5548.