Quantitative insulin sensitivity check index: A simple, accurate method for assessing insulin sensitivity in humans

Insulin resistance plays an important role in the pathophysiology of diabet es and is associated with obesity and other cardiovascular risk factors. Th e "gold standard" glucose clamp and minimal model analysis are two establis hed methods for determining insulin sensitivity in vivo, but neither is eas ily implemented in large studies. Thus, it is of interest to develop a simp le, accurate method for assessing insulin sensitivity that is useful for cl inical investigations. We performed both hyperinsulinemic isoglycemic gluco se clamp and insulin-modified frequently sampled iv glucose tolerance tests on 28 nonobese, 13 obese, and 15 type 2 diabetic subjects. We obtained cor relations between indexes of insulin sensitivity from glucose clamp studies (SIClamp) and minimal model analysis (SIMM) that were comparable to previo us reports (r = 0.57). We performed a sensitivity analysis on our data and discovered that physiological steady state values [i.e. fasting insulin (I- 0) and glucose (G(0))] contain critical information about insulin sensitivi ty. We defined a quantitative insulin sensitivity check index (QUICKI = 1/[ log(I-0) + log(G(0))]) that has substantially better correlation with SIcla mp (r = 0.78) than the correlation we observed between SIMM andSI(clamp). M oreover, we observed a comparable overall correlation between QUICKI and SI Clamp in a totally independent group of 21 obese and 14 nonobese subjects f rom another institution. We conclude that QUICKI is an index of insulin sen sitivity obtained from a fasting blood sample that may be useful for clinic al research.