Use of glycated haemoglobin A1c for diagnosing diabetes in Chinese subjects aged over 50 years-community based observation

Background: The performance of glycated haemoglobin A(1)c (HbA(1)c) for diagnosing diabetes in Chinese subjects remains uncertain. Our study aims to assess HbA(1)c for the diagnosis of diabetes and identify the cutpoint to be used in Chinese subjects aged over 50 years. Methods: From Oct 2010 to Jan 2011, we conducted a community-based cross-sectional survey in Shipai community, Guangzhou, China. A total of 1494 subjects over 50 years old were recruited. Each subject completed a uniform questionnaire and had a physical examination. Fasting blood samples were obtained to measure plasma glucose and HbA(1)c. Diabetes is defined as fasting plasma glucose (FPG) of at least 7.0 mmol/L. One hundred and sixty-one subjects with diagnosed diabetes and 21 with missing data were excluded and data of 1312 subjects were analysed. Receiver operating characteristics (ROC) curve were plotted to assess the sensitivity and specificity of HbA(1)c for diagnosing diabetes. Results: Among 1312 subjects, 53 subjects (4.0%) had diabetes, 88 subjects (6.7%) had IFG, 10.7% had hyperglycemia (diabetes plus IFG). According to the ROC curves, the area under the curve for HbA(1)c in diagnosing diabetes was 0.945 (0.931-0.957). An HbA(1)c threshold of 48 mmol/mol (6.5%) showed the highest combination of sensitivity (83.3%) and specificity (96.0%) for diagnosing diabetes. Conclusion: An HbA(1)c threshold of 48 mmol/mol (6.5%) could be used for diagnosing diabetes in Chinese aged over 50 years. This threshold may be proper as a diagnostic criterion for diabetes in Chinese over 50 years old.