Correlations Between HbA1c, Fasting Glucose,2h Postload Glucose And β-cell Function In The Chinese Population

Objective:This study was aimed to assess the associations of hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), and 2h postload plasma glucose (2hPG) with β-cell function in the Chinese population.Methods:A total of 913 subjects, who underwent 75-g OGTT for evaluation of glucose intolerance from June 2010 to February 2013, were included. According to OGTT, the enrolled subjects were divided into the following three groups:normal glucose tolerance (NGT, n=205), isolated-impaired fasting glucose (IFG, n=72), isolated-impaired glucose tolerance(IGT, n=125) and type 2 diabetes mellitus (T2DM, n=380). Meanwhile, the subjects were also divided into three groups according to HbAlc levels:HbAlc<5.7% (n=277), HbAlc 5.7-6.4%(n=391), and HbAlc≥6.5 (n=245). Insulin sensitivity was measured by Matsuda insulin sensitivity index (ISIM) and 1/homeostasis model assessment of insulin resistance (1/HOMA-IR). Insulin release was calculated by basal HOMA-β, early-phase InsAUC3o/GluAUC30, and total-phase InsAUC120/GluAUC120. β-cell function relative to insulin sensitivity was expressed as disposition index (DI).Results:All indices of insulin sensitivity and β-cell function gradually decreased with increasing HbAlc, FPG, and 2hPG (all P<0.01). Compared with HbAlc, FPG showed stronger correlations with HOMA-β, InsAUC3o/GluAUC3o, InsAUC120/GluAUC120, DI30, and DI120 (all P<0.05), and 2hPG was more closely related to DI30 and DI120 (all P<0.01). Moreover, FPG was more strongly related to HOMA-β and InsAUC30/GluAUC30 than 2hPG (all P<0.05). The combination of IFG and HbAlc 5.7-6.4% showed the greatest reduction in DI30 and DI120 compared with HbAlc 5.7-6.4% alone, i-IGT, or i-IFG (P<0.05).Conclusions:HbAlc could be used as a marker to identify subjects with impaired β-cell function, but OGTT performs better than HbA1c. The combination of HbAlc and FPG is a simple and sensitive method to evaluate β-cell function.