Objective: We investigated the cutoff values of surrogate measures of insulin resistance for diagnosing metabolic syndrome in Korean adults.
Research Design and Methods: This study was conducted as part of the Korean Metabolic Syndrome (KMS) Study. The data from 976 non-diabetic individuals (484 men and 492 women) aged 30~79 years were analyzed. We determined the odds ratios for the prevalence of metabolic syndrome according to the quartiles of fasting insulin, homeostasis model assessment ofr insulin resistance (HOMA-IR), and quanititative insulin sensitivity check index (QUICKI) as independent variables, while adjusting for age, sex, and body mass index. The areas under the receiver-operating characteristic (ROC) curves for fasting insulin, HOMA-IR, and QUICKI for increased metabolic syndrome were compared, and the cutoff values of fasting insulin, HOMA-IR, and QUICKI were estimated.
Results: The cutoff points for defining insulin resistance are a fasting insulin level of 12.94 uU/mL, HOMA-IR = 3.04 as the 75th percentile value, and QUICKI = 0.32 as the 2.5th percentile value. Compared with the lowest quartile, the adjusted odds ratios for the prevalence of metabolic syndrome in the highest quartiles of fasting insulin, HOMA-IR, and QUICKI were 1.95(1.26~3.01), 2.27(1.45~3.56), and 2.27(1.45~3.56), respectively. The respective cutoff values for fasting serum insulin, HOMA-IR, and QUICKI by ROC analysis were 10.57 uU/mL (sensitivity 58.5%, specificity 66.8%), 2.34 (sensitivity 62.8%, specificity 65.7%), and 0.33 (sensitivity 61.2%, specificity 66.8%).
Conclusions: Fasting insulin, HOMA-IR, and QUICKI are good surrogate measures of insulin resistance in Korean non-diabetic adults. We suggest that the cutoff values using these simple methods could be applied to evaluate insulin resistance and predict metabolic syndrome in Korean non-diabetic adults.

Keywords: Insulin resistance, Metabolic syndrome, Insulin, HOMA, QUICKI