(01-10-10) Performance of Glycated Hemoglobin for the Classification and Prediction of Diabetes.

Selvin E, Steffes MW, Gregg E, Brancati FL, Coresh J.

Department of Epidemiology and the Welch Center for Prevention, Epidemiology
and Clinical Research, Johns Hopkins Bloomberg School of Public Health,
Baltimore, MD.
Abstract
AbstractBackground: Although glycated hemoglobin (HbA1c) is now recommended to
diagnose diabetes, its test performance for diagnosis and prognosis is
uncertain. Our objective was to assess the test performance of HbA1c against
single and repeat glucose measurements for diagnosis of prevalent diabetes and
for prediction of incident diabetes. Design and Methods: Population-based
analyses of 12,485 participants The Atherosclerosis Risk in Communities (ARIC)
Study and a subpopulation of 691 participants in the Third National Health and
Nutrition Examination Survey (NHANES III) with repeat test results. Results:
Against a single fasting glucose ??126 mg/dl, the sensitivity (Sn) and
specificity (Sp) of HbA1c ??6.5% for detection of prevalent diabetes were 47%
and 98%, respectively (AUC 0.892). Against repeated fasting glucose (3 years
apart) ??126 mg/dl, Sn improved to 67% and Sp remained high (97%) (AUC 0.936).
Similar results were obtained in NHANES III against repeated fasting glucose 2
weeks apart. The accuracy of HbA1c was consistent across age, BMI, and race
groups. For persons with fasting glucose ??126 mg/dl and HbA1c ??6.5% at
baseline, the 10-year risk of diagnosed diabetes was 88% as compared to 55%
among those persons with fasting glucose ??126 mg/dl and HbA1c 5.7-<6.5%.
Conclusions: HbA1c performs well as a diagnostic tool when diabetes definitions
that most closely resemble those used in clinical practice are used as the gold
standard. The high risk of diabetes among initially undiagnosed persons with
both elevated fasting glucose and HbA1c suggests a dual role for fasting
glucose and HbA1c for prediction of diabetes.

Source: Diabetes Care. 2010 Sep 20. [Epub ahead of print]

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