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

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.