Upper limit of fasting plasma glucose level defined by oral glucose tolerance test in Japanese subjects.

There are conflicting interpretations regarding the normal fasting plasma glucose level in Japanese subjects. We therefore aimed to define the upper limit of fasting plasma glucose level.A total of 962 subjects who had a 75-g oral glucose tolerance test were examined. Subjects were divided into two groups - post-load normal glycemic group (2-h plasma glucose <140 mg/dL) and post-load hyperglycemic group (2-h plasma glucose≥140 mg/dL).There were 434 subjects with post-load normal glycemia and 528 subjects with post-load hyperglycemia. Receiver operating characteristic curve (ROC) demonstrated that the optimal cut-off value for predicting post-load hyperglycemia was a fasting plasma glucose of 99 mg/dL (area under ROC curve=0.81), which had a sensitivity, specificity, and overall diagnostic accuracy of 68%, 81%, 74%, respectively.These data suggest that for predicting post-load hyperglycemia, the optimal cut-off value of fasting plasma glucose was 99 mg/dL in Japanese subjects. Thus, the current cut-off value of fasting plasma glucose of 110 mg/dL in Japan might be lowered.