title: Is a single bioelectrical impedance equation valid for children of wide ranges of age, pubertal status and nutritional status? Evidence from the 4-component model.
abstract: OBJECTIVE
  Bioelectrical impedance analysis (BIA) is widely used to predict body composition in paediatric research and clinical practice. Many equations have been published, but provide inconsistent predictions.
  
  
  OBJECTIVE
  To test whether a single equation for lean mass (LM) estimation from BIA is appropriate across wide ranges of age, pubertal status and nutritional status, by testing whether specific groups differ in the slope or intercept of the equation.
  
  
  METHODS
  In 547 healthy individuals aged 4-24 years (240 males), we collected data on body mass (BM) and height (HT), and lean mass (LM) using the 4-component model. Impedance (Z) was measured using TANITA BC418MA instrumentation. LM was regressed on HT(2)/Z. Multiple regression analysis was conducted to investigate whether groups based on gender, age, pubertal status or nutritional status differed in the association of LM with HT(2)/Z.
  
  
  RESULTS
  BM ranged from 5 to 128 kg. HT(2)/Z was a strong predictor of LM (r (2)=0.953, s.e.e.=2.9 kg). There was little evidence of a sex difference in this relationship, however, children aged 4-7 years and 16-19 years differed significantly from other age groups in regression slopes and intercepts. Similar variability was encountered for pubertal stage, but not for nutritional status.
  
  
  CONCLUSIONS
  No single BIA equation applies across the age range 4-24 years. At certain ages or pubertal stages, the slope and intercept of the equation relating LM to HT(2)/Z alters. Failure to address such age effects is likely to result in poor accuracy of BIA (errors of several kg) for longitudinal studies of change in body composition.
authors.affiliation: Childhood Nutrition Research Centre, UCL Institute of Child Health, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Montagnese
authors.forename: J E
authors.initials: JE
authors.lastname: Williams
authors.forename: D
authors.initials: D
authors.lastname: Haroun
authors.forename: M
authors.initials: M
authors.lastname: Siervo
authors.forename: M S
authors.initials: MS
authors.lastname: Fewtrell
authors.forename: J C K
authors.initials: JC
authors.lastname: Wells
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000886:Anthropometry / Q000379:methods*; D001823:Body Composition; D001825:Body Fluid Compartments; D001835:Body Weight; D002648:Child; D002675:Child, Preschool; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D055641:Mathematical Concepts; D008954:Models, Biological; D009752:Nutritional Status; D011627:Puberty; D012044:Regression Analysis; D055815:Young Adult