Expanding the clinical use of standard OGTT: the percentage increment of 2 h with respect to fasting glucose as an index of β-cell dysfunction.

Aims Since glucose levels during oral glucose tolerance test (OGTT) are determined both by insulin sensitivity and insulin secretion, we investigated whether the percentage increment (PG%) of 2-h plasma glucose (2hPG) over fasting plasma glucose (FPG) is related to validated indexes of insulin sensitivity and insulin secretion. Methods Using Stumvoll's formulas we calculated estimated insulin sensitivity index and first-phase insulin secretion in 1281 subjects who underwent a standard OGTT. The ratio first-phase insulin secretion/(1/estimated insulin sensitivity index) was considered a surrogate index of β-cell function. For each subject we calculated PG% using the formula: [(2hPG − FPG)/FPG] × 100. For each glucose tolerance group we formed tertiles based on PG% values. Results In each glucose tolerance group, β-cell function was better preserved in lower PG% tertiles, demonstrating a correlation between PG% and insulin resistance. Conclusions By a simple calculation, our study allows, expansion of the clinical use of OGTT to recognize subjects liable to further worsening of glucose homeostasis, independent from glucose tolerance groupings. Copyright © 2011 John Wiley & Sons, Ltd.