Validity of Glycated Hemoglobin in Screening and Diagnosing Type 2 Diabetes Mellitus in Chinese Subjects

Background/Aims: The application of glycated hemoglobin ($HbA_{1c}$) for the diagnosis of diabetes is currently under extensive discussion. In this study, we explored the validity of using $HbA_{1c}$ as a screening and diagnostic test in Chinese subjects recruited in Nanjing, China. Methods: In total, 497 subjects (361 men and 136 women) with fasting plasma glucose (PG) ${\geq}\;5.6 mmol/L$ were recruited to undergo the oral glucose tolerance test (OGTT) and $HbA_{1c}$ test. Plasma lipid, uric acid, and blood pressure were also measured. Results: Using a receiver operating characteristic curve, the optimal cutoff point of $HbA_{1c}$ related to diabetes diagnosed by the OGTT was 6.3%, with a sensitivity and specificity of 79.6% and 82.2%, respectively, and the area under the curve was 0.87 (95% confidence interval, 0.83 to 0.92). A $HbA_{1c}$ level of 6.5% had a sensitivity and specificity of 62.7% and 93.5%, respectively. When comparing the $HbA_{1c}$ ${\geq}\;6.5%$ or OGTT methods for diagnosing diabetes, the former group had significantly higher $HbA_{1c}$ levels and lower levels of fasting and 2-hour PG than the latter group. No significant difference was observed in the other metabolism indexes between the two groups. Conclusions: Our results suggest that $HbA_{1c}$ ${\geq}\;6.5%$ has reasonably good specificity for diagnosing diabetes in Chinese subjects, which is in concordance with the American Diabetes Association recommendations.