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

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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.