Reproducibility of the Oral Glucose Tolerance Test in Overweight Children

J Clin Endocrinol Metab. 2008 Nov;93(11):4231-7. doi: 10.1210/jc.2008-0801. Epub 2008 Aug 19.

Abstract

Objective: We examined the reproducibility of the oral glucose tolerance test (OGTT) in overweight children and evaluated distinguishing characteristics between those with concordant vs. discordant results.

Design: Sixty overweight youth (8-17 yr old) completed two OGTTs (interval between tests 1-25 d). Insulin sensitivity was assessed by the surrogate measures of fasting glucose to insulin ratio, whole-body insulin sensitivity index, and homeostasis model assessment of insulin resistance, and insulin secretion by the insulinogenic index with calculation of the glucose disposition index (GDI).

Results: Of the 10 subjects with impaired glucose tolerance (IGT) during the first OGTT only three (30%) had IGT during the second OGTT. The percent positive agreement between the first and second OGTT was low for both impaired fasting glucose and IGT (22.2 and 27.3%, respectively). Fasting blood glucose had higher reproducibility, compared with the 2-h glucose. Youth with discordant OGTTs, compared with those with concordant results, were more insulin resistant (glucose/insulin 2.7+/-1.4 vs. 4.1+/-1.8, P=0.006, whole-body insulin sensitivity index of 1.3+/-0.6 vs. 2.2+/-1.1, P=0.003, and homeostasis model assessment of insulin resistance 10.6+/-8.1 vs. 5.7+/-2.8, P=0.001), had a lower GDI (0.45+/-0.58 vs. 1.02+/-1.0, P=0.03), and had higher low-density lipoprotein cholesterol (117.7+/-36.6 vs. 89.9+/-20.1, P=0.0005) without differences in physical characteristics.

Conclusions: Our results show poor reproducibility of the OGTT in obese youth, in particular for the 2-h plasma glucose. Obese youth who have discordant OGTT results are more insulin resistant with higher risk of developing type 2 diabetes mellitus, as evidenced by a lower GDI. The implications of this remain to be determined in clinical and research settings.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adolescent
  • Blood Glucose / metabolism
  • Body Mass Index
  • C-Peptide / blood
  • Child
  • Fasting
  • Female
  • Glucose / administration & dosage*
  • Glucose Intolerance / blood
  • Glucose Intolerance / diagnosis
  • Glucose Tolerance Test / standards*
  • Humans
  • Insulin / blood
  • Insulin / metabolism
  • Insulin Resistance
  • Insulin Secretion
  • Male
  • Obesity / blood*
  • Overweight / blood*
  • Puberty
  • Reproducibility of Results

Substances

  • Blood Glucose
  • C-Peptide
  • Insulin
  • Glucose