Ideal glycated hemoglobin cut‐off points for screening diabetes and prediabetes in a Chinese population

AIMS/INTRODUCTION: The aims of the present study were to evaluate the diagnostic value of fasting plasma glucose, 2‐h postload plasma glucose and glycosylated hemoglobin (HbA1c) measurements in the screening of diabetes and prediabetes, and to determine the cut‐off point of HbA1c in the diagnosis of diabetes and prediabetes in a Chinese population. MATERIALS AND METHODS: A total of 7,611 individuals aged 40 years or older, who did not have a prior history of diabetes, were randomly selected in the Changchun area. For each participant, a questionnaire was completed, and a physical examination and an oral glucose tolerance test were carried out. The values of fasting plasma glucose, 2‐h postload plasma glucose and HbA1c were compared by area under the receiver operating characteristic curves. The Youden index was used to identify the optimal cut‐off point of HbA1c in the diagnosis of diabetes and prediabetes. RESULTS: The prevalence of newly diagnosed diabetes and prediabetes was 12.71% and 29.39%, respectively. In participants with newly diagnosed diabetes, the area under the receiver operating characteristic curve was 0.8368 for fasting plasma glucose, 0.9330 for 2‐h postload plasma glucose and 0.8064 for HbA1c; whereas for prediabetes, these values were 0.8022, 0.9288 and 0.6895, respectively. In addition, an HbA1c threshold of 6.3% showed the highest Youden index (0.4799) for detecting diabetes; furthermore, an HbA1c threshold of 5.8% showed the highest Youden index (0.2866) for detecting prediabetes. CONCLUSIONS: HbA1c ≥6.3% (45 mmol/mol) and between 5.8% and 6.2% (40–44 mmol/mol) were the optimal cut‐off values for the diagnosis of diabetes and prediabetes, respectively, in a Chinese population.