Measuring Insulin Sensitivity in Youth: How Do the Different Indices Compare with the Gold-Standard Method?

Aim. - The objective of the study was to examine the correlation between three methods of measuring insulin sensitivity (IS) namely, the frequently sampled intravenous glucose tolerance test (FSIVGTT), indices derived from the oral glucose tolerance test (OGTT) and fasting indices (HOMA-IR, QUICKI, fasting insulin [INS0])-and the gold-standard method, the hyperinsulinaemic-euglycaemic clamp (HEC) test, in children.Methods. - A total of 20 children [nine boys and 11 girls; mean (SD) age: 9 (2) years] were studied. Their mean (SD) BMI Z score was 1.5 (0.8). All participants had normal glucose metabolism. Each child underwent a 3-h HEC (40 mU/m(2)/min of insulin), an insulin-modified minimal-model FSIVGTT and a 3-h OGTT. The clamp-derived IS was calculated, using DeFronzo's metabolized glucose index and Bergman's IS index. Correlations were established using Spearman's rank correlations.Results. - The two clamp-derived measures were highly correlated (r=0.85), and the IS measured from the FSIVGTT was well correlated with both clamp measures [r=0.69, 0.74]. Of the nine indices derived from the OGTT, the three with the highest correlation with clamp results were the IST Matsuda [r=0.63, 0.68], SI(is)OGTT [r=0.53, 0.65] and log sum insulin [r=-0.64, 0.75]. Fasting indices of IS had similar correlations to clamp results: HOMA-IR [r=-0.55, -0.56]; QUICKI [r=0.55, 0.57]; and INS0 [r=-0.59, -0.63].Conclusion. - While fasting-based indices of IS are a suitable option for large cohorts, OGTT-derived indices may represent a useful compromise for obtaining both clinical (glucose tolerance) and physiological (insulin sensitivity) information, making them particularly useful for large-scale physiological and epidemiological studies. (C) 2010 Elsevier Masson SAS. All rights reserved.