Repeatability characteristics of insulin response patterns and measures of insulin resistance

Catherine A.P Crofts,Mark C Wheldon,Caryn Zinn,Fabrice Merien,Grant Schofield

doi:10.4102/jir.v4i1.44

Abstract

Background: Hyperinsulinaemia is emerging as an independent risk factor for metabolic disease, but diagnostic measures are limited. It is plausible that insulin resistance measures, such as homeostatic model assessment (HOMA) type 2 variants, may model hyperinsulinaemia, but repeatability data are limited. Kraft and Hayashi insulin response patterns may not only add value in diagnosing hyperinsulinaemia, but also lack suitable repeatability data.Aim: The aim of this study was to investigate the repeatability of insulin response patterns, and fasting and dynamic measures of insulin resistance, and to determine whether these latter measures can predict the insulin response pattern.Setting: This study was conducted at Auckland University of Technology Millennium Institute’s sports performance laboratories.Methods: Oral glucose (100 g) tolerance tests were conducted weekly on eight people. Six people completed four tests, while two completed at least two tests. Each test assessed insulin resistance and response patterns. Insulin resistance measures included fasting tests (HOMA2, McAuley Index) and a dynamic test (oral glucose insulin sensitivity [OGIS]). The insulin response patterns were assessed with both Kraft and Hayashi methodologies. Repeatability characteristics of ordinal variables were assessed by Bland and Altman methods, while Fleiss’ κ was applied to categorical variables.Results: Fasting measures of insulin resistance recorded poor repeatability (HOMA2) or poor sensitivity (McAuley Index) compared to the dynamic measure (OGIS). Kraft insulin response patterns were more repeatable compared to Hayashi patterns, based on a combination of Fleiss’ κ (0.290 vs. 0.186,) p-value (0.15 vs. 0.798) and 95% confidence intervals.Conclusions: Both hyperinsulinaemia and insulin resistance should be dynamically assessed with a multi-sampled oral glucose tolerance test. Further investigations are required to confirm a preferred methodology.

Highlights

Insulin resistance is recognised as being a significant risk factor for type 2 diabetes and other metabolic diseases
‘Dynamic’ methods are derived from a combination of fasting and post-prandial testing during an oral glucose tolerance test (OGTT) and include oral glucose insulin sensitivity (OGIS)
Ten participants consented to the study, but only eight participants completed at least two tests; results are included for the latter eight participants

Summary

Introduction

Insulin resistance is recognised as being a significant risk factor for type 2 diabetes and other metabolic diseases. Insulin resistance measures do not add value to disease risk calculations.[1,2] People with insulin resistance generally have chronic hyperinsulinaemia to compensate for poor glucose uptake rates. The gold-standard method for assessing insulin resistance is the hyperinsulinaemic-euglycaemic clamp (HIEG) This method is often impractical, especially in clinical settings or with large cohorts, so alternative methods are often used that model the HIEG. It is plausible that insulin resistance measures, such as homeostatic model assessment (HOMA) type 2 variants, may model hyperinsulinaemia, but repeatability data are limited. Kraft and Hayashi insulin response patterns may add value in diagnosing hyperinsulinaemia, and lack suitable repeatability data

Objectives

Methods

Results