Failure of mathematical indices to accurately assess insulin resistance in lean, overweight, or obese women with polycystic ovary syndrome

Insulin resistance is a common metabolic feature of polycystic ovary syndrome (PCOS). In this study, we examined the validity of the mathematical indices [the quantitative insulin sensitivity check index (QUICKI) and the homeostasis model of assessment (HOMA)] that calculate insulin sensitivity and their correlation to glucose utilization with the insulin infusion rate in 40 mU/m(2).min by the euglycemic clamp (M) in women with PCOS. We studied 59 women with PCOS (20 lean, 16 overweight, and 23 obese subjects). Euglycemic clamp testing was performed, and QUICKI, HOMA, total testosterone, fasting insulin, fasting glucose, and glucose-to-insulin ratio were estimated. No difference was found in testosterone and glucose levels among the three groups. Lean or overweight women compared with obese women differed in insulin levels, glucose-to-insulin ratio, QUICKI, and HOMA (P < 0.01). No statistical difference was found between lean and overweight women in the above parameters. M differed when lean women were compared with overweight (P < 0.002) or obese women (P < 0.0001); however, no statistical difference was observed between overweight and obese women. No significant correlation was found between M and QUICKI or HOMA. We conclude that mathematical indices should be applied with caution in different insulin-resistant populations and should not be considered a priori equivalent to the euglycemic clamp technique.