A1C for Screening and Diagnosis of Type 2 Diabetes in Routine Clinical Practice
- Zhong X. Lu, PHD1,2,
- Karen Z. Walker, PHD3,4,
- Kerin O'Dea, PHD5,
- Ken A. Sikaris, FRCPA1 and
- Jonathan E. Shaw, MD6
- 1Melbourne Pathology Services, Melbourne, Australia;
- 2Department of Medicine, Monash Medical Centre, Monash University, Melbourne, Australia;
- 3Department of Nutrition and Dietetics, Monash University, Melbourne, Australia;
- 4Preventative Health Unit, Baker IDI Heart and Diabetes Institute, Melbourne, Australia;
- 5Sansom Institute for Health Research, University of South Australia, Adelaide, Australia;
- 6Clinical Diabetes and Epidemiology Unit, Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
- Corresponding author: Zhong X. Lu, zhong.lu{at}mps.com.au.
Abstract
OBJECTIVE To evaluate A1C for screening and diagnosis of undiagnosed type 2 diabetes defined by oral glucose tolerance testing in clinical and general populations.
RESEARCH DESIGN AND METHODS A1C cut offs (≤5.5% to rule out diabetes; ≥7.0% to rule in diabetes) were derived from a clinical group (Melbourne Pathology [MP] group: n = 2,494; undiagnosed diabetes 34.6%) and then evaluated in a population-based sample (AusDiab group: n = 6,015; undiagnosed diabetes 4.6%).
RESULTS For diabetes in the MP and AusDiab groups, A1C at 5.5% gave sensitivities of 98.7 and 83.5%, while A1C at 7.0% gave specificities of 98.2 and 100%, respectively. Many (61.9–69.3%) with impaired A1C (5.6–6.9%) in both populations had abnormal glucose status.
CONCLUSIONS A1C ≤5.5% and ≥7.0% predicts absence or presence of type 2 diabetes, respectively, while at A1C 6.5–6.9% diabetes is highly probable in clinical and population settings. A high proportion of people with impaired A1C have abnormal glucose status requiring follow-up.
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 September 21, 2009.
- Accepted January 6, 2010.
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.
