Glycosylated Hemoglobin Threshold for Predicting Diabetes and Prediabetes from the Fifth Korea National Health and Nutrition Examination Survey

We aimed to estimate the threshold level of glycosylated hemoglobin (HbA1c) for the fasting plasma glucose of 100 and 126 mg/dL in the Korean adult population, using the 2011 Korea National Health and Nutrition Examination Survey. A total of 4,481 participants over 19 years of age without diabetic medications and conditions to influence the interpretation of HbA1c levels, such as anemia, renal insufficiency, liver cirrhosis, and cancers, were analyzed. A point-wise area under the receiver operating characteristic curve was used to estimate the optimal HbA1c cutoff value. A HbA1c threshold of 6.35% was optimal for predicting diabetes with a sensitivity of 86.9% and a specificity of 99.1%. Furthermore, the threshold of HbA1c was 5.65% for prediabetes, with a sensitivity of 69.3% and a specificity of 71%. Further prospective studies are needed to evaluate the HbA1c cutoff point for diagnosing prediabetes and diabetes in the Korean population.