title: Repeatability characteristics of simple indices of insulin resistance: implications for research applications.
abstract: The objectives of this study were to evaluate test characteristics, such as normality of distribution, variation, and repeatability, of simple fasting measures of insulin sensitivity and to use the results to choose among these measures. Duplicate fasting samples of insulin and glucose were collected before 4 h of euglycemic hyperinsulinemic clamping using insulin infusion rates ranging from 40-600 mU/m2 x min. Currently recommended estimates of insulin sensitivity, including the fasting insulin, 40/insulin, the homeostasis model assessment, the logarithmic transformation of the homeostasis model assessment, and the Quantitative Insulin Sensitivity Check Index, were evaluated. The normality of distribution and the variability of the tests (coefficient of variation and discriminant ratio) were compared between the measures and against the "gold standard" hyperinsulinemic clamp. Data from 253 clamp studies in 152 subjects were examined, including 79 repeated studies for repeatability analysis. In subjects ranging from lean to diabetic, the log transformed fasting measures combining insulin and glucose had normal distributions and test characteristics superior to the other simple indices (logarithmic transformation of the homeostasis model assessment coefficient of variation, 0.55; discriminant ratio, 13; Quantitative Insulin Sensitivity Check Index coefficient of variation, 0.05; discriminant ratio, 10) and statistically comparable to euglycemic hyperinsulinemic clamps (coefficient of variation, 0.10; discriminant ratio, 6.4). These favorable characteristics helped explain the superior correlations of these measures with the hyperinsulinemic clamps among insulin-resistant subjects. Furthermore, therapeutic changes in insulin sensitivity were as readily demonstrated with these simple measures as with the hyperinsulinemic clamp. The test characteristics of the logarithmic transformation of the homeostasis model assessment and the Quantitative Insulin Sensitivity Check Index are superior to other simple indices of insulin sensitivity. This helps explain their excellent correlations with formal measures both at baseline and with changes in insulin sensitivity and supports their broader application in clinical research.
authors.affiliation: Indiana University School of Medicine, Division of Endocrinology and Metabolism, Indianapolis, Indiana 46250, USA. kmather@iupui.edu
authors.forename: K J
authors.initials: KJ
authors.lastname: Mather
authors.forename: A E
authors.initials: AE
authors.lastname: Hunt
authors.forename: H O
authors.initials: HO
authors.lastname: Steinberg
authors.forename: G
authors.initials: G
authors.lastname: Paradisi
authors.forename: G
authors.initials: G
authors.lastname: Hook
authors.forename: A
authors.initials: A
authors.lastname: Katz
authors.forename: M J
authors.initials: MJ
authors.lastname: Quon
authors.forename: A D
authors.initials: AD
authors.lastname: Baron
mesh_terms: D000328:Adult; D000465:Algorithms; D015415:Biomarkers; D001786:Blood Glucose / Q000378:metabolism; D016208:Databases, Factual; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D009765:Obesity / Q000378:metabolism; D012016:Reference Values; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin