title: Clinical relevance of inter-method differences in fat-free mass estimation in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Evaluation of fat-free mass (FFM) is becoming recognised as an important component in the assessment of clinical status and formulation of prognosis in patients with chronic obstructive pulmonary disease (COPD).
  
  
  OBJECTIVE
  The aim of this study was to determine whether potential differences in FFM estimation performed by air displacement plethysmography (ADP), bioelectrical impedance (BIE) and anthropometry (ANTHRO) would assume clinical significance.
  
  
  METHODS
  Twenty-eight patients with moderate-to-severe COPD were submitted to FFM estimation by ADP, BIE and ANTHRO. FFM was then allometrically related to peak oxygen uptake (peak VO2) as determined by symptom-limited incremental cycle ergometry.
  
  
  RESULTS
  We found that ANTHRO classified fewer patients as 'FFM-depleted' than the other two techniques (p < 0.05). Although mean biases of the BIE-ADP differences were close to zero, their 95% confidence limits extended as high as 5.9 kg (16%). The ANTHRO-based allometric exponents for peak VO2 correction of FFM, therefore, were typically higher than those obtained by the other two methods in both depleted and non-depleted patients (ANTHRO: 1.45-1.41, BIE: 0.97-1.18, ADP: 1.08-1.14, respectively).
  
  
  CONCLUSIONS
  We conclude that between-method differences in FFM estimation can be sufficiently large to have practical implications in patients with moderate-to-severe COPD. A single method of body composition assessment, therefore, should be used for FFM estimation in these patients.
authors.affiliation: Centre for Exercise Science and Medicine, Institute of Biological and Life Sciences, University of Glasgow, UK.
authors.forename: Liam P
authors.initials: LP
authors.lastname: Kilduff
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Fuld
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
authors.forename: Yannis P
authors.initials: YP
authors.lastname: Pitsiladis
authors.forename: Roger
authors.initials: R
authors.lastname: Carter
authors.forename: Robin
authors.initials: R
authors.lastname: Stevenson
authors.forename: Susan A
authors.initials: SA
authors.lastname: Ward
mesh_terms: D000368:Aged; D000886:Anthropometry; D001823:Body Composition / Q000502:physiology*; D017097:Electric Impedance; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology; D010991:Plethysmography / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*