Utility of hemoglobin A1c in detecting risk of type 2 diabetes: comparison of hemoglobin A1c with other biomarkers.

We have previously reported that the risk of type 2 diabetes, early impaired glucose tolerance, and insulin resistance can be predicted using fasting levels of adiponectin, leptin, and insulin. Here, we aimed to evaluate the utility of hemoglobin A1c in detecting the risk of type 2 diabetes compared with other well-known biomarkers. We randomly enrolled 207 volunteers with no history of diseases, who underwent 75-g oral glucose tolerance tests and were stratified into normal, borderline, abnormal, or diabetic groups. Eighty-one participants with normal baseline levels of hemoglobin A1c (<6.0%) were included in the normal groups of both glucose tolerance and insulin resistance. Hemoglobin A1c was significantly correlated with the plasma glucose and insulin resistance index. Leptin, adiponectin, glycoalbumin, and body mass index also were correlated well with plasma glucose levels and insulin resistance index. Normal hemoglobin A1c levels with abnormal glucose tolerance and insulin resistance were noted in 85 and 67 participants, respectively. Hemoglobin A1c did not strengthen the prediction algorithm of diabetes, determined by our proposed biomarkers, leptin, adiponectin, and insulin. In conclusion, hemoglobin A1c is a surrogate biomarker for risk of diabetes, with inadequate predictive value, and should be used in combination with other biomarkers.