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 center dot min(-1) center dot m(-2) insulin infusion) M value in 147 women ( 58 - 61 years; BMI 19 - 38 kg/m(2); 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 D approximate to 0 for all variables. The best surrogates of M were OGIS ( one D. 0) and MCRest ( two D. 0); the other methods either under- or overestimated the degree of correlation three or more D. 0), in particular with fasting insulin (HOMA: D=- 57%; ISIcomp: D=- 36%) and BMI ( HOMA: D=- 14%; ISIcomp: D=- 14%; SiORAL: D=- 11%). Conclusions/interpretation: AllIS 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