Comparison of Oral and Intravenous Glucose Tolerance Test Derived Sensitivity and Secretory Indices in Obese Adolescents

Abstract

Background. Insulin resistance increases type 2 diabetes risk in obese adolescents. Thus, quantitative tools measuring insulin sensitivity and secretion are important for risk assessment. Methods. Forty-four obese pubertal adolescents underwent oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test (FSIGT). We correlated OGTT-derived whole body sensitivity index (WBISI) with FSIGT-derived insulin sensitivity index (Si). Insulinogenic index (IGI) from OGTT was compared with acute insulin response to glucose (AIRg) from FSIGT. Results. Fasting insulin ( r = −.64, P < .0005) and glucose ( r = −.39 P ≤ .0005) predicted Si. The OGTT-derived index WBISI correlated with the FSIGT-derived Si ( r = .608, P < .0005). IGI correlated with AIRg from FSIGT ( r = .704, P < .0005). Conclusions. OGTT-based measures correlated with FSIGT-derived measures of insulin sensitivity and secretion. In particular, we demonstrated that WBISI can be a reliable alternative to FSIGT-derived Si in clinical settings where OGTT is a more feasible option.