Lipoprotein Insulin Resistance Index: A Simple, Accurate Method for Assessing Insulin Resistance in South Asians

Abstract

Background Identification of insulin resistance (IR) in South Asians (SA), who are at a higher risk for type 2 diabetes is important. Lack of standardization of insulin assays limits the clinical use of insulin-based surrogate indices. The lipoprotein insulin resistance index (LP-IR), a metabolomic marker, reflects the lipoprotein abnormalities observed in IR. The reliability of the LP-IR index in SA is unknown. Objective We evaluated the predictive accuracy of LP-IR compared to other IR-surrogate indices in SA. Methods In a cross-sectional study (n = 55), we used calibration model analysis to assess the ability of the LP-IR score and other simple surrogate indices [HOMA-IR, QUICKI, Adipose insulin resistance index (Adipo-IR), and Matsuda Index] to predict insulin sensitivity (S_I) derived from the reference frequently sampled intravenous glucose tolerance test. LP-IR index was derived from lipoprotein particle concentrations and sizes measured by nuclear magnetic resonance spectroscopy. Predictive accuracy was determined by root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE). The optimal cut-off of LP-IR index was determined by the area under the receiver operating characteristic curve (AUC-ROC) and the Youden index. Results The simple surrogate indices showed moderate correlations with S_I (r = 0.53-0.69, p < 0.0001). CVPE and RMSE were not different in any of the surrogate indices when compared to LP-IR. The AUC-ROC was 0.77 (95% CI 0.64–0.89). The optimal cut-off for IR in SA was LP-IR >48 (sensitivity: 75%, specificity: 70%). Conclusions LP-IR index is a simple, accurate, and clinically useful test to assess IR in South Asians.