Author(s): Mann DM, Carson AP, Shimbo D, Fonseca V, Fox CS,
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Abstract OBJECTIVE: New clinical practice recommendations include A1C as an alternative to fasting glucose as a diagnostic test for identifying pre-diabetes. The impact of these new recommendations on the diagnosis of pre-diabetes is unknown. RESEARCH DESIGN AND METHODS: Data from the National Health and Nutrition Examination Survey 1999-2006 (n = 7,029) were analyzed to determine the percentage and number of U.S. adults without diabetes classified as having pre-diabetes by the elevated A1C (5.7-6.4\%) and by the impaired fasting glucose (IFG) (fasting glucose 100-125 mg/dl) criterion separately. Test characteristics (sensitivity, specificity, and positive and negative predictive values) using IFG as the reference standard were calculated. RESULTS: The prevalence of pre-diabetes among U.S. adults was 12.6\% by the A1C criterion and 28.2\% by the fasting glucose criterion. Only 7.7\% of U.S. adults, reflecting 61 and 27\% of those with pre-diabetes by A1C and fasting glucose, respectively, had pre-diabetes according to both definitions. A1C used alone would reclassify 37.6 million Americans with IFG to not having pre-diabetes and 8.9 million without IFG to having pre-diabetes (46.5 million reclassified). Using IFG as the reference standard, pre-diabetes by the A1C criterion has 27\% sensitivity, 93\% specificity, 61\% positive predictive value, and 77\% negative predictive value. CONCLUSIONS: Using A1C as the pre-diabetes criterion would reclassify the pre-diabetes diagnosis of nearly 50 million Americans. It is imperative that clinicians and health systems understand the differences and similarities in using A1C or IFG in diagnosis of pre-diabetes.
This article was published in Diabetes Care
and referenced in Journal of Diabetes & Metabolism