Prediction of insulin resistance in type 2 diabetes mellitus using routinely available clinical parameters

Abstract

Aims

To determine if insulin resistance (IR), an important predictor of cardiovascular risk in the general population and in type 2 diabetes mellitus, can be assessed using simple parameters which are readily available in clinical practice.

Methods

This cross-sectional study included 194 patients with type 2 diabetes. Body mass index, waist index (WI), triglyceride levels, 1/HDL, triglyceride/HDL, uric acid and urine albumin:creatinine ratio were investigated as possible predictors of IR.

Results

WI correlated more strongly than any other parameter with log insulin levels, log fasting glucose to insulin ratio (FGIR), log fasting glucose to insulin product (FGIP), homeostatic model assessment (HOMA-IR) and quantitative insulin check index (QUICKI). WI also emerged as the strongest independent predictor of IR indices studied in regression as well as in ROC analyses. At a cut-off of 1.115, WI had a 78% sensitivity and 65% specificity for predicting IR when HOMA-IR was used as indicator of IR, and 74% sensitivity and specificity when QUICKI was used as indicator of IR. Combining WI with other variables did not improve performance significantly.

Conclusions

In our cohort of patients with type 2 diabetes, WI was the parameter with the strongest association with, and the best predictor of, IR.

Introduction

Insulin resistance (IR) is a pathological condition characterized by inadequate peripheral tissue metabolic response to circulating insulin, and plays an important pathophysiological role in type 2 diabetes mellitus (T2DM). Furthermore, IR is associated with atherosclerosis [1], [2] and results in a number of metabolic and haemodynamic disturbances that are collectively referred to as the metabolic syndrome. IR is also an important predictor of cardiovascular morbidity and mortality both in the general population [3], [4] and in patients with T2DM [5], [6]. It is also associated with increased cancer mortality independent of diabetes [6].

The gold standard method for measurement of IR is the euglycaemic hyperinsulinaemic clamp [7], whereby the rate of whole-body glucose disposal during steady-state hyperinsulinaemia is assessed. However, this technique is costly, time-consuming and metabolically invasive, making it impractical to use in large cross-sectional or longitudinal studies or in clinical practice. Simple indices have thus been developed and validated for quantification of IR, based on measurement of fasting plasma insulin and glucose levels and calculated with different mathematical formulas. These include the homeostatic model assessment (HOMA-IR) [8], the quantitative insulin sensitivity check index (QUICKI) [9], fasting glucose to insulin ratio (FGIR) and fasting insulin glucose product (FIGP). These are better suited for use in clinical studies. Nonetheless, since insulin levels are not routinely measured in clinical practice, they are still of limited value. Hence, in spite of the important clinical implications of IR, it cannot be readily detected.

The goal of the present study is to assess how variables which are more readily available in routine clinical practice are associated with IR in a cohort of adults with T2DM and whether they can be used to predict IR.