Published in:
01-01-2010 | Article
An empirical index of insulin sensitivity from short IVGTT: validation against the minimal model and glucose clamp indices in patients with different clinical characteristics
Published in: Diabetologia | Issue 1/2010
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Aims/hypothesis
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.
Methods
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 (SI) and the mean glucose infusion rate (clamp) (M). A calculated SI (CSI) predictor, \({\text{CS}}_{{\text{I}}} = {\text{ $ \alpha $ }} \times {K_{\text G} } \mathord{\left/ {\vphantom {{K_{G} } {{\left( {{\Delta {\text{AUC}}_{{{\text{INS}}}} } \mathord{\left/ {\vphantom {{\Delta {\text{AUC}}_{{{\text{INS}}}} } T}} \right. \kern-\nulldelimiterspace} T} \right)}}}} \right. \kern-\nulldelimiterspace} {{\left( {{\Delta {\text{AUC}}_{{{\text{INS}}}} } \mathord{\left/ {\vphantom {{\Delta {\text{AUC}}_{{{\text{INS}}}} } T}} \right. \kern-\nulldelimiterspace} T} \right)}}\), was suggested, based on the calculation of the rate of glucose disappearance K
G and the suprabasal AUC of insulin concentration ΔAUCINS over T = 40 min. For all the participants, α was assumed equal to the regression line slope between K
G/(ΔAUCINS/T) and SI in control participants.
Results
CSI and SI showed high correlation (R
2 = 0.68–0.96) and regression line slopes of approximately one in the majority of groups. CSI tended to overestimate SI in type 2 diabetic participants, but results were more reliable when CSI was computed with insulin-modified rather than regular IVGTT. CSI showed behaviours similar to SI as regards relationships with BMI, acute insulin response and sex. CSI showed good correlation with M (R
2 = 0.82).
Conclusions/interpretation
A short test can achieve a good approximation of minimal model analysis and clamp insulin sensitivity. The importance of a method such as CSI is that it allows analysis of IVGTT datasets with samples limited to 1 h.