title: Indexes of insulin resistance and secretion in obese children and adolescents: a validation study.
abstract: OBJECTIVE
  To assess the concurrent validity of fasting indexes of insulin sensitivity and secretion in obese prepubertal (Tanner stage 1) children and pubertal (Tanner stages 2-5) adolescents using estimates from the modified minimal model frequently sampled intravenous glucose tolerance test (FSIVGTT) as a criterion measure.
  
  
  METHODS
  Eighteen obese children and adolescents (11 girls and 7 boys, mean age 12.2 +/- 2.4 years, mean BMI 35.4 +/- 6.2 kg/m(2), mean BMI-SDS 3.5 +/- 0.5, 7 prepubertal and 11 pubertal) participated in the study. All participants underwent an insulin-modified FSIVGTT on two occasions, and 15 repeated this test a third time (mean 12.9 and 12.0 weeks apart). S(i) measured by the FSIVGTT was compared with homeostasis model assessment (HOMA) of insulin resistance (HOMA-IR), quantitative insulin-sensitivity check index (QUICKI), fasting glucose-to-insulin ratio (FGIR), and fasting insulin (estimates of insulin sensitivity derived from fasting samples). The acute insulin response (AIR) measured by the FSIVGTT was compared with HOMA of percent beta-cell function (HOMA-beta%), FGIR, and fasting insulin (estimates of insulin secretion derived from fasting samples).
  
  
  RESULTS
  There was a significant negative correlation between HOMA-IR and S(i) (r = -0.89, r = -0.90, and r = -0.81, P < 0.01) and a significant positive correlation between QUICKI and S(i) (r = 0.89, r = 0.90, and r = 0.81, P < 0.01) at each time point. There was a significant positive correlation between FGIR and S(i) (r = 0.91, r = 0.91, and r = 0.82, P < 0.01) and a significant negative correlation between fasting insulin and S(i) (r = -90, r = -0.90, and r = -0.88, P < 0.01). HOMA-beta% was not as strongly correlated with AIR (r = 0.60, r = 0.54, and r = 0.61, P < 0.05).
  
  
  CONCLUSIONS
  HOMA-IR, QUICKI, FGIR, and fasting insulin correlate strongly with S(i) assessed by the FSIVGTT in obese children and adolescents. Correlations between HOMA-beta%, FGIR and fasting insulin, and AIR were not as strong. Indexes derived from fasting samples are a valid tool for assessing insulin sensitivity in prepubertal and pubertal obese children.
authors.affiliation: Department of Endocrinology and Diabetes, Royal Children's Hospital, Herston, Brisbane, Queensland, Australia. louise_conwell@health.qld.edu.au
authors.forename: Louise S
authors.initials: LS
authors.lastname: Conwell
authors.forename: Stewart G
authors.initials: SG
authors.lastname: Trost
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Brown
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Batch
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D002648:Child; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D009765:Obesity / Q000097:blood* / Q000503:physiopathology*; D011627:Puberty; D011793:Queensland; D015203:Reproducibility of Results; D044465:White People
chemical_list: D001786:Blood Glucose; D007328:Insulin