title: Bioelectric impedance spectroscopy underestimates fat-free mass compared to dual energy X-ray absorptiometry in incurable cancer patients.
abstract: OBJECTIVE
  Weight loss is frequently seen in advanced cancer. Bioelectrical impedance spectroscopy (BIS) is a convenient method for estimating body composition. We examined in a prospective, comparative study if BIS could accurately estimate fat-free mass (FFM) in cancer patients compared to dual-energy X-ray absorptiometry (DXA).
  
  
  METHODS
  The study was based on 132 consecutive incurable cancer patients with solid tumours in a University hospital outpatient clinic. Comparison of FFM from DXA and BIS with standard and revised equations. Bland-Altman plots, t-tests and linear regression analysis were used to evaluate agreement and differences between methods.
  
  
  RESULTS
  BIS significantly underestimated mean FFM with 7.6+/-4.7 kg compared to DXA (P<0.001). Bias was significantly correlated to % weight loss (r=0.32), systemic inflammation as measured by C-reactive protein (r=0.29), malnutrition as assessed by low insulin-like growth factor-1 (r=-0.23) and inversely to the per cent body fat estimated by DXA (P=-0.61) and body mass index (BMI; r=-0.30). Revised BIS equations taking BMI into account reduced bias significantly but still with great individual variation.
  
  
  CONCLUSIONS
  BIS by standard equations grossly underestimates FFM compared to DXA in cancer patients. This bias is related to weight loss, malnutrition and systemic inflammation. Revised equations improved FFM estimates, but with large individual variation. Thus, BIS with standard equations is not suitable to estimate FFM in patients with cachexia, inflammation and malnutrition.
authors.affiliation: Department of Clinical Nutrition, Sahlgrenska University Hospital, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden. Lasse.Ellegard@nutrition.gu.se
authors.forename: L H
authors.initials: LH
authors.lastname: Ellegård
authors.forename: M
authors.initials: M
authors.lastname: Ahlén
authors.forename: U
authors.initials: U
authors.lastname: Körner
authors.forename: K G
authors.initials: KG
authors.lastname: Lundholm
authors.forename: L D
authors.initials: LD
authors.lastname: Plank
authors.forename: I G
authors.initials: IG
authors.lastname: Bosaeus
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000273:Adipose Tissue; D001825:Body Fluid Compartments; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis; D002100:Cachexia / Q000209:etiology; D018450:Disease Progression; D017097:Electric Impedance; D006801:Humans; D007334:Insulin-Like Growth Factor I; D016014:Linear Models; D044342:Malnutrition / Q000209:etiology; D009369:Neoplasms / Q000150:complications / Q000503:physiopathology*; D015203:Reproducibility of Results; D013057:Spectrum Analysis / Q000379:methods*; D019452:Terminally Ill; D015431:Weight Loss
chemical_list: D007334:Insulin-Like Growth Factor I; D002097:C-Reactive Protein