Comparison between HOMA-IR and ISI-gly in detecting subjects with the metabolic syndrome

To verify whether, as index of insulin resistance, ISI-gly (insulin sensitivity index) is more efficient than HOMA-IR (homeostatic model assessment) or QUICKI (quantitative insulin sensitivity check index) in detecting patients with the metabolic syndrome.

Excluding patients with known diabetes, endocrine, liver and kidney diseases, we enrolled 553 subjects who were screened for metabolic abnormalities. After 5 days of a balanced weight maintenance diet, we performed an OGTT (oral glucose tolerance test) and measured fasting and 2-h postload blood sugar and insulin, from which we calculated ISI-gly, HOMA-IR and QUICKI, stratifying patients in tertiles. Statistical comparisons were performed for a number of metabolic variables between tertiles of the same index, as well as between tertiles of different indexes presumably expressing identical insulin resistance.

All variables reflecting the metabolic syndrome were significantly more altered in the top as compared to the intermediate and the lowest tertile for HOMA-IR, the opposite for ISI-gly. Comparing homologous measurements of the top tertile of HOMA-IR with the lowest tertile of ISI-gly (presumably expressing identical insulin resistance), fasting glucose and insulin were significantly higher, while 2-h OGTT values were significantly lower. The opposite occurred comparing the lowest HOMA-IR to the highest ISI-gly tertile, the diagnostic predictive values of the latter in detecting metabolic derangements being also higher. Data from QUICKI 1st to 3rd tertiles exactly matched those obtained from HOMA-IR 3rd to 1st tertile.

ISI-gly, which includes postload glucose and insulin concentrations, provides a more accurate estimate of whole-body insulin sensitivity than HOMA-IR or QUICKI, derived from fasting measurements only, thus constituting a more sensitive tool for screening and preventing metabolic abnormalities.