Glycated Haemoglobin in Diagnosis of Diabetes Mellitus and Pre-diabetes among Middle-aged and Elderly Population: Shanghai Changfeng Study*

Abstract Objective To investigate the optimal glycated haemoglobin (HbA1c) cut off points and evaluate the impact of HbA1c on diabetes and pre-diabetes in middle-aged and elderly population. Methods Subjects were recruited from Shanghai Changfeng Study. A total of 1 973 community-based participants (age≥45) without known diabetes underwent oral glucose tolerance test (OGTT) by using a 75-g oral glucose load and HbA1c was measured by using high performance liquid chromatography (HPLC). Subjects were classified as normal glucose tolerance (NGT), pre-diabetes(impaired glucose regulation, IGR) and new diagnosed diabetes (NDD) per 1999 WHO criteria. Two tests are compared with receiver operating characteristic curve (ROC). Results Among 1973 subjects, 271 (13.7%) were diagnosed as NDD and 474 (24.0%) as IGR by using OGTT. HbA1c was 5.7%±0.7% in this population. Use of 6.5% as the HbA1C cutoff point has sensitivity of 38.7% and specificity of 98.5%. We recommend 6.0% as a better cutoff value for diagnosis of diabetes in this population (AUC 0.829, 95% CI 0.798-0.860, P Conclusion The optimum HbA1c cutoff point for diabetes in our study population was lower than ADA criteria, and HbA1c may not be used to identify IGR.