Repeatability of Indices of Insulin Sensitivity and Secretion from Standard Liquid Meal Tests in Subjects with Type 2 Diabetes Mellitus or Normal or Impaired Fasting Glucose

Background: The objective of this investigation was to evaluate the test-retest repeatability of insulin sensitivity and secretion indices derived from liquid meal tolerance tests (MTTs) in subjects with normal fasting glucose (NFG) (n - 20), impaired fasting glucose (IFG) (n - 20), or type 2 diabetes mellitus (n - 38). Methods: The Matsuda Index of insulin sensitivity and a Disposition Index (the product of the Matsuda Index and the ratio of the total areas under the curves for glucose and insulin from 0 to 120 min) were assessed in two standard liquid MTTs, separated by approximately 1 week. Results: Mean +/- SD Matsuda Index values were 14.2 +/- 7.6, 8.8 +/- 4.7, and 6.3 +/- 4.0, and Disposition Index values were 1,009.6 +/- 355.5, 671.4 +/- 249.0, and 201.8 +/- 101.3 for NFG, IFG, and diabetes, respectively (all P < 0.05 except Matsuda Index for IFG vs. diabetes, P = 0.241). Differences between tests in subjects with NFG, IFG, and diabetes, respectively, were -0.2 +/- 3.6 (coefficient of variation for the method error, 17.9%), 0.2 +/- 3.2 (26.1%), and 0.1 +/- 3.0 (34.1%) for the Matsuda Index and 16.5 +/- 225.8 (16.1%), 13.3 +/- 221.6 (23.1%), and 15.2 +/- 79.4 (28.1%) for the Disposition Index. Conclusions: The Matsuda and Disposition indices derived from liquid MTTs appropriately ranked categories of fasting glucose tolerance and have repeatability profiles suggesting potential usefulness in population studies and moderately sized clinical trials requiring repeated measurements.