Correlation between fasting plasma glucose and two-hour plasma glucose during oral glucose tolerance test in South...

The diagnostic criteria for diabetes have been recently revised and the fasting plasma glucose (FPG) level reduced to 126 mg/dL, since the earlier cutoff of 140 mg/dL was considered to correspond to a much higher level than the 2-hour postglucose (2 h PG) value of 200 mg/dL. However, there are few data directly correlating FPG and 2 h PG during an oral glucose tolerance test (OGTT). This study reports on a retrospective analysis of 5,936 OGTTs performed at a diabetes center in South India and attempts to correlate the FPG and 2 h PG values. Using a 2 h PG of 200 mg/dL or higher as the diagnostic criterion, 46.7% of the cohort had diabetes. The corresponding values using the old FPG of 140 mg/dL or higher and the new FPG of 126 mg/dL or higher were 31.7% and 39.8%, respectively. If the FPG was further reduced to 118 mg/dL, the "diabetic yield" increased to 45.8%, ie, it approached the figures based on a 2 h PG of > or =200 mg/dL. Various regression equations were used to correlate FPG and 2 h PG values. When FPG was used as the dependent variable, the semilogarithmic regression equation provided the best fit, and using this model, the 2 h PG of 200 mg/dL corresponds to a FPG of 118 mg/dL. When the 2 h PG was used as the dependent variable, the log-log model provided the best fit, and using this model, a 2 h PG of 200 mg/dL corresponds to a FPG of 118 mg/dL. Thus, a FPG of 118 mg/dL seems to correlate with a 2 h PG of 200 mg/dL in South Indians.