We investigated the association between postchallenge glucose increment and hemoglobin glycation index (HGI), the difference between observed and predicted glycated hemoglobin (HbA1c), in subjects with no history of diabetes. We enrolled 1381 subjects who attended our outpatient clinic for an oral glucose tolerance test (OGTT) to screen for diabetes. HGI was defined as observed HbA1c minus predicted HbA1c. The predicted HbA1c was calculated by entering fasting plasma glucose (FPG) level into an equation [HbA1c(%)=FPG(mg/dL)*0.029+2.9686] determined from an HbA1c versus FPG regression analysis using data from an independent cohort of 2734 subjects with no history of diabetes. The association between 2-hour glucose increment and HGI was analyzed using linear regression analyses with adjustment of relevant parameters. Overall, the proportions of subjects with normal glucose tolerance, pre-diabetes, and newly diagnosed diabetes were 42.3%, 41.3%, and 16.4%, respectively. Compared with subjects who had an HGI <= 0, subjects with an HGI>0 had a lower FPG (95.0 +/- 13.3 vs 98.5 +/- 15.3 mg/dL, p<0.001) but a higher 2-hour plasma glucose (151.1 +/- 52.8 vs 144.6 +/- 51.4 mg/dL, p=0.027) and 2-hour glucose increment (56.1 +/- 46.1 vs 46.1 +/- 45.0 mg/dL, p<0.001). The 2-hour glucose increment after an OGTT was independently associated with HGI (beta coefficient 0.003, 95% CI 0.002 to 0.003, p<0.001). Our findings suggested that postchallenge glucose increment was independently associated with HGI in subjects with no history of diabetes.
