title: Comparison of two bioelectrical impedance devices and dual-energy X-ray absorptiometry to evaluate body composition in heart failure.
abstract: BACKGROUND
  The utilisation of bioelectrical impedance analysis (BIA) in heart failure can be affected by many factors and its applicability remains controversial. The present study aimed to verify the adequacy of single-frequency BIA (SF-BIA) and multifrequency BIA (MF-BIA) compared to dual-energy x-ray absorptiometry (DEXA) for evaluating body composition in outpatients with heart failure.
  
  
  METHODS
  In this cross-sectional study, 55 patients with stable heart failure and left ventricle ejection fraction ≤45% were evaluated for fat mass percentage, fat mass and fat-free mass by DEXA and compared with the results obtained by SF-BIA (single frequency of 50 kHz) and MF-BIA (frequencies of 20 and 100 kHz).
  
  
  RESULTS
  MF-BIA and DEXA gave similar mean values for fat mass percentage, fat mass and fat-free mass, whereas values from SF-BIA were significantly different from DEXA. Both SF-BIA and MF-BIA measures of body composition correlated strongly with DEXA (r > 0.8; P < 0.001), except for fat mass assessed by SF-BIA, which showed a moderate correlation (r = 0.760; P < 0.001). MF-BIA also showed a better agreement with DEXA by Bland-Altman analysis in all measurements. However, both types of equipment showed wide limits of agreement and a significant relationship between variance and bias (Pitmans's test P > 0.05), except MF-BIA for fat-free mass.
  
  
  CONCLUSIONS
  Compared with DEXA, MF-BIA showed better accuracy than SF-BIA, although both types of equipment showed wide limits of agreement. The BIA technique should be used with caution, and regression equations might be useful for correcting the observed variations, mainly in extreme values of body composition.
authors.affiliation: Post-Graduate Program in Cardiovascular Sciences, Faculty of Medicine, Federal University of Rio Grande do Sul, Porto, Alegre, Brazil; Department of Internal Medicine, Faculty of Medicine, Federal University of Rio Grande do Sul, Porto, Alegre, Brazil.
authors.forename: F D
authors.initials: FD
authors.lastname: Alves
authors.forename: G C
authors.initials: GC
authors.lastname: Souza
authors.forename: A
authors.initials: A
authors.lastname: Biolo
authors.forename: N
authors.initials: N
authors.lastname: Clausell
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000378:metabolism; D000368:Aged; D001823:Body Composition; D001825:Body Fluid Compartments; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006333:Heart Failure / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged
keywords: bioelectrical impedance; body composition; dual-energy X-ray absorptiometry; heart failure