HbA1c for screening and diagnosis of Type 2 diabetes in routine clinical practice
- Zhong X Lu, (PhD) (zhong.lu{at}mps.com.au)1,2,
- Karen Z Walker, (PhD)3,4,
- Kerin O'Dea, (PhD)6,
- Ken A Sikaris, (FRCPA)1 and
- Jonathan E Shaw, (MD)5
- 1Melbourne Pathology Services, Melbourne, Australia
- 2Department of Medicine, Monash Medical Centre and
- 3Department of Nutrition and Diabetes, Monash University, Melbourne
- 4Preventative Health Unit and
- 5Clinical Diabetes and Epidemiology Unit, Baker IDI Heart and Diabetes Institute, Melbourne
- 6Sansom Institute for Health Research, University of South Australia, Adelaide, Australia
Abstract
Objective- To evaluate HbA1c for screening and diagnosis of undiagnosed Type 2 diabetes defined by oral glucose tolerance testing in clinical and general populations.
Research design and methods- HbA1c cut-offs (≤5.5% to ‘rule-out’; ≥7.0% to ‘rule-in’ diabetes) were derived from a clinical group (MP: n= 2,494; undiagnosed diabetes 34.6%) and then evaluated in a population-based sample (AusDiab: n=6,015, undiagnosed diabetes 4.6%).
Results- For diabetes in MP and AusDiab, HbA1c at 5.5% gave sensitivities of 98.7% and 83.5%, while HbA1c at 7.0% gave specificities of 98.2% and 100%, respectively. Many (61.9 – 69.3%) with impaired HbA1c (IA1c: 5.6 – 6.9%) in both populations had abnormal glucose status.
Conclusions- HbA1c ≤5.5% and ≥7.0% predicts absence or presence of Type 2 diabetes while at HbA1c 6.5–6.9%, diabetes is highly probable in clinical and population settings. A high proportion of people with IA1c have abnormal glucose status requiring follow-up.
Footnotes
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- Received September 21, 2009.
- Accepted January 6, 2010.
- Copyright © American Diabetes Association
