Comparative evaluation of simple insulin sensitivity methods based on the oral glucose tolerance test

Aims/hypothesis We compared five surrogate insulin sensitivity (IS) methods against the euglycaemic–hyperinsulinaemic clamp. These methods were the homeostasis model assessment (HOMA) and four methods based on the OGTT (OGIS, MCRest, ISIcomp, SIORAL).Methods We compared these IS methods against the clamp (0.28 nmol·min^–1·m^–2 insulin infusion) M value in 147 women (58–61 years; BMI 19–38 kg/m²; 116 NGT, 25 IFG/IGT, six type 2 diabetic), by evaluating the correlation coefficient with M. We also tested the ability to reproduce the relationships between IS and typical IS correlates (BMI, fasting insulin, insulin to glucose OGTT area ratio and fasting, 2 h and mean glucose) by means of the discrepancy index D, in which (1) D=0 if the correlation between IS and the variable of interest is as with the clamp, (2) D is smaller than 0 if the correlation is overestimated, and (3) D is greater than 0 if underestimated.Results All IS methods correlated with M (r=0.57–0.83, p<0.0001); for MCRest the relationship was markedly curvilinear. All IS measures correlated with the considered variables (r=0.29–0.94, p<0.0005); however, no method had D0 for all variables. The best surrogates of M were OGIS (one D0) and MCRest (two D0); the other methods either under- or overestimated the degree of correlation (three or more D0), in particular with fasting insulin (HOMA: D=–57%; ISIcomp: D=–36%) and BMI (HOMA: D=–14%; ISIcomp: D=–14%; SiORAL: D=–11%).Conclusions/interpretation All IS methods were correlated with M. OGIS and MCRest were preferable to the other methods and in particular to HOMA for reproducing relationships with the independent variables.