Minimal model analysis for insulin sensitivity has been validated against the glucose clamp and is an accepted method for estimating insulin sensitivity from IVGTT. However minimal model analysis requires a 3 h test and relevant expertise to run the mathematical model. The aim of this study was to suggest a simple predictor of minimal model analysis index using only 1 h IVGTT.

We studied participants with different clinical characteristics who underwent 3 h regular (n = 336) or insulin-modified (n = 160) IVGTT, or 1 h IVGTT and euglycaemic–hyperinsulinaemic clamp (n = 247). Measures of insulin sensitivity were insulin sensitivity index estimated by minimal model analysis (S_I) and the mean glucose infusion rate (clamp) (M). A calculated S_I (CS_I) predictor, ${\text{CS}}_{{\text{I}}} = {\text{ ${\text{CS}}_{{\text{I}}} = {\text{ , was suggested, based on the calculation of the rate of glucose disappearance K _G and the suprabasal AUC of insulin concentration ΔAUC_INS over T = 40 min. For all the participants, α was assumed equal to the regression line slope between K _G/(ΔAUC_INS/T) and S_I in control participants.

CS_I and S_I showed high correlation (R ² = 0.68–0.96) and regression line slopes of approximately one in the majority of groups. CS_I tended to overestimate S_I in type 2 diabetic participants, but results were more reliable when CS_I was computed with insulin-modified rather than regular IVGTT. CS_I showed behaviours similar to S_I as regards relationships with BMI, acute insulin response and sex. CS_I showed good correlation with M (R ² = 0.82).

A short test can achieve a good approximation of minimal model analysis and clamp insulin sensitivity. The importance of a method such as CS_I is that it allows analysis of IVGTT datasets with samples limited to 1 h.