Diagnosing insulin resistance by simple quantitative methods in subjects with normal glucose metabolism.

OBJECTIVE: To identify a reliable yet simple indirect method for detection of insulin resistance (IR). RESEARCH DESIGN AND METHODS: A total of 65 subjects (44 men and 21 women aged 30-60 years) were selected by a simple random sampling method. Inclusion criteria were voluntary participation from staff and hospital personnel, absence of abnormal glucose tolerance, and normal results of lipid profile and basic blood chemistry. A blood sample was taken after a 12-h overnight fast to determine plasma lipid, glucose, and insulin levels. An intravenous glucose tolerance test with administration of insulin after 20 min and extraction of multiple blood samples for glucose and insulin measurements and calculation of the minimal model approximation of the metabolism of glucose (MMAMG) S(i) value were performed. Three indirect indexes used to predict insulin sensitivity or IR were calculated, and metabolic syndrome was diagnosed using the Adult Treatment Panel III (ATP III) criteria. All results were correlated with those of the MMAMG.
RESULTS: The 75th percentile value as the cutoff point to define IR corresponded with a fasting plasma glucose level of 12 mU/l, a homeostasis model assessment of 2.6, a 25th percentile for S(i) value of 21, and QUICKI (quantitative insulin sensitivity check index) and McAuley indexes of 0.33 and 5.8, respectively. The S(i) index correlated (P < 0.001) with all the indirect indexes and parameters of the metabolic syndrome.
CONCLUSIONS: When compared with the S(i) index, the most sensitive and specific indirect method was the score proposed by McAuley et al. (specificity 0.91, sensitivity 0.75, 9.2 probability ratio of a positive test), followed by the existence of metabolic syndrome (specificity 0.91, sensitivity 0.66, 7.8 probability ratio of a positive test).