2. In the second step, after exclusion of subjects with self-reported diabetes, we classified the screened subjects into 3 groups according to their fasting plasma glucose concentration of 7.0 mmol/L or above, 5.0 to 6.9 mmol/L or below 5.0 mmol/L. We selected randomly a sample from these 3 subgroups for further investigation including a 75-g oral glucose tolerance test (OGTT) and blood and urine sampling and other vascular functional measurements. Our selection was based on a ratio of 1:1.2:1.44, because of the concern that by knowing the results of fasting plasma glucose test, subjects with lower glucose levels might have a lower participation rate than those with higher glucose concentrations. Nevertheless, this ratio was arbitrarily chosen. Finally, 1000 Type 2 diabetic patients, 1200 subjects with IGR and 1440 subjects with normal glucose metabolism were selected as target population of this study by random sampling for further blood and urine sampling.