title: Validity of bioelectrical impedance analysis to assess fat-free mass in patients with head and neck cancer: an exploratory study.
abstract: BACKGROUND
  The purpose of this study was to validate bioelectrical impedance analysis (BIA) using the Geneva equation for fat-free mass (FFM) in patients with head and neck cancer.
  
  
  METHODS
  In 24 patients with head and neck cancer, agreement between BIA (FFMBIA ) and dual energy x-ray absorptiometry (FFMDXA ) 1 week before (T0 ), 1 month (T1 ), and 4 months (T2 ) after cancer treatment was analyzed.
  
  
  RESULTS
  FFMBIA did not differ from FFMDXA (mean difference 0.71 ± 1.9, 0.30 ± 1.9, and 0.02 ± 2.1 kg) at any time point. Only at T0 , mean FFM correlated to the difference between FFMDXA and FFMBIA (r = 0.48; p = .017). Limits of agreement were 3.8, 3.7, and 4.1 kg, respectively. Concordance Correlation Coefficients were 0.98 at all time points.
  
  
  CONCLUSIONS
  BIA may be used to assess FFM with reasonable validity based on mean-level comparisons, but differences between BIA and DXA may vary by about 4 kg in an individual patient. These results require confirmation in a larger sample of patients with head and neck cancer.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Hanze University of Applied Sciences, Professorship in Health Care and Nursing, Groningen, The Netherlands.
authors.forename: Harriët
authors.initials: H
authors.lastname: Jager-Wittenaar
authors.forename: Pieter U
authors.initials: PU
authors.lastname: Dijkstra
authors.forename: Carrie P
authors.initials: CP
authors.lastname: Earthman
authors.forename: Wim P
authors.initials: WP
authors.lastname: Krijnen
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Langendijk
authors.forename: Bernard F A M
authors.initials: BF
authors.lastname: van der Laan
authors.forename: Jan
authors.initials: J
authors.lastname: Pruim
authors.forename: Jan L N
authors.initials: JL
authors.lastname: Roodenburg
mesh_terms: D015502:Absorptiometry, Photon; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology; D017097:Electric Impedance; D005260:Female; D006258:Head and Neck Neoplasms / Q000503:physiopathology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D044342:Malnutrition / Q000175:diagnosis* / Q000503:physiopathology; D008875:Middle Aged; D015596:Nutrition Assessment
keywords: bioelectrical impedance analysis; body composition; fat-free mass; head and neck cancer; validity