title: Reproducibility of serum leptin, insulin-like growth factor-I, and insulin-like growth factor-binding protein-3 measurements.
abstract: BACKGROUND
  Many epidemiologic studies examine the effects of single measurements of hormones, including those related to obesity such as insulin-like growth factors (IGFs) or leptin, on disease associations; however, few studies have determined whether these single values accurately reflect measurements over time.
  
  
  METHODS
  We examined the reproducibility of hormones associated with obesity, specifically leptin, IGF-I, and IGF-binding protein-3 (IGFBP-3). Two fasting blood samples, approximately four months apart, were collected from 38 participants from the Seattle metropolitan area; leptin, IGF-I, and IGFBP-3 concentrations were measured in previously unthawed serum samples. Unadjusted and adjusted intraclass correlation coefficients (ICC) were calculated to assess reproducibility.
  
  
  RESULTS
  Adjusting for age and sex, the ICCs for leptin, IGF-I, and IGFBP-3 were 0.73, 0.83 and 0.60, respectively. Weighted kappas yielded similar results.
  
  
  CONCLUSIONS
  These data suggest that for leptin, IGF-I, and IGFBP-3, a single fasting serum measurement can fairly reliably reflect the hormonal milieu over periods of months.
authors.affiliation: Cancer Prevention Program, Fred Hutchinson Cancer Research Center, Seattle, Wash. 98109, USA.
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Chia
authors.forename: Polly A
authors.initials: PA
authors.lastname: Newcomb
authors.forename: Emily
authors.initials: E
authors.lastname: White
authors.forename: Yingye
authors.initials: Y
authors.lastname: Zheng
authors.forename: John D
authors.initials: JD
authors.lastname: Potter
authors.forename: Johanna W
authors.initials: JW
authors.lastname: Lampe
mesh_terms: D000328:Adult; D001835:Body Weight; D005215:Fasting / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000032:analysis* / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D020738:Leptin / Q000032:analysis* / Q000097:blood; D008297:Male; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012107:Research Design
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D020738:Leptin; D007334:Insulin-Like Growth Factor I