[Comparison of HbA1c and oral glucose tolerance test for diagnosing diabetes].

OBJECTIVE: To compare the performance of glycated hemoglobin (HbA1c) and oral glucose tolerance test (OGTT) in diagnosing diabetes and pre-diabetes in the general population. METHODS: A total of 1416 subjects from Nanchang, Jiangxi Province and Wuhan, Hubei Province who have participated the 2010 Chinese Nutrition and Health Survey were studied and their HbA1c were measured. The glycemic levels and distribution of the subjects diagnosed with diabetes and pre-diabetes by OGTT and HbA1c were compared. Receiver operating characteristic curves were constructed to determine the sensitivity and specificity of HbA1c in detecting diabetes as defined by OGTT. RESULTS: According to the 1999 WHO criteria, 86 subjects were diagnosed with diabetes and 262 were with pre-diabetes. Comparing with OGTT, the sensitivity and specificity of HbA1c > or = 6.5% was 41.9% and 98.9%. Subjects with diabetes diagnosed by HbA1c and OGTT were not consistent, and they have different HbA1c level. The HbA1c level of 5.7% - 6.4% was associated with a sensitivity of 78.6% and a specificity of 55.1% in detecting impaired glucose regulation (IGR). Cases with pre-diabetes identified by HbA1c 5.7% - 6.4% were different from those with IGR. They had lower fasting glucose and 2-hour plasma glucose after glucose load than those with IGR. CONCLUSION: Among this studied population, HbA1c > or = 6.5% showed high specificity but low sensitivity for detecting glucose-defined diabetes. The performance of HbA1c of 5.7% -6.4% in screening pre-diabetes is poor.