title: Body composition in dialysis patients: a functional assessment of bioimpedance using different prediction models.
abstract: OBJECTIVE
  The assessment of body composition (BC) in dialysis patients is of clinical importance given its role in the diagnosis of malnutrition and sarcopenia. Bioimpedance techniques routinely express BC as a 2-compartment (2-C) model distinguishing fat mass (FM) and fat-free mass (FFM), which may be influenced by the hydration of adipose tissue and fluid overload (OH). Recently, the BC monitor was introduced which applies a 3-compartment (3-C) model, distinguishing OH, adipose tissue mass, and lean tissue mass. The aim of this study was to compare BC between the 2-C and 3-C models and assess their relation with markers of functional performance (handgrip strength [HGS] and 4-m walking test), as well as with biochemical markers of nutrition.
  
  
  METHODS
  Forty-seven dialysis patients (30 males and 17 females) (35 hemodialysis, 12 peritoneal dialysis) with a mean age of 64.8 ± 16.5 years were studied. 3-C BC was assessed by BC monitor, whereas the obtained resistivity values were used to calculate FM and FFM according to the Xitron Hydra 4200 formulas, which are based on a 2-C model.
  
  
  RESULTS
  FFM (3-C) was 0.99 kg (95% confidence interval [CI], 0.27 to 1.71, P = .008) higher than FFM (2-C). FM (3-C) was 2.43 kg (95% CI, 1.70-3.15, P < .001) lower than FM (2-C). OH was 1.4 ± 1.8 L. OH correlated significantly with ΔFFM (FFM 3-C - FFM 2-C) (r = 0.361; P < .05) and ΔFM (FM 3-C - FM 2-C) (r = 0.387; P = .009). HGS correlated significantly with FFM (2-C) (r = 0.713; P < .001), FFM (3-C) (r = 0.711; P < .001), body cell mass (2-C) (r = 0.733; P < .001), and body cell mass (3-C) (r = 0.767; P < .001). Both physical activity (r = 0.456; P = .004) and HGS (r = 0.488; P = .002), but not BC, were significantly related to walking speed.
  
  
  CONCLUSIONS
  Significant differences between 2-C and 3-C models were observed, which are partly explained by the presence of OH. OH, which was related to ΔFFM and ΔFM of the 2-C and 3-C models, is therefore an important parameter for the differences in estimation of BC parameters of the 2-C and 3-C models. Both FFM (3-C) and FFM (2-C) were significantly related to HGS. Bioimpedance, HGS, and the 4-m walking test may all be valuable tools in the multidimensional nutritional assessment of both hemodialysis and peritoneal dialysis patients.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands.
authors.forename: Natascha J H
authors.initials: NJ
authors.lastname: Broers
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands.
authors.forename: Remy J H
authors.initials: RJ
authors.lastname: Martens
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: Cornelis
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands.
authors.forename: Nanda M P
authors.initials: NM
authors.lastname: Diederen
authors.affiliation: Fresenius Medical Care D GmbH, Research and Development, Bad Homburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Wabel
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands.
authors.forename: Frank M
authors.initials: FM
authors.lastname: van der Sande
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands.
authors.forename: Karel M L
authors.initials: KM
authors.lastname: Leunissen
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands. Electronic address: jeroen.kooman@mumc.nl.
authors.forename: Jeroen P
authors.initials: JP
authors.lastname: Kooman
mesh_terms: D000273:Adipose Tissue / Q000502:physiology; D001823:Body Composition / Q000502:physiology*; D001826:Body Fluids / Q000502:physiology; D017097:Electric Impedance; D005080:Exercise Test / Q000706:statistics & numerical data; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys / Q000706:statistics & numerical data*; D009752:Nutritional Status / Q000502:physiology*; D006435:Renal Dialysis; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology* / Q000628:therapy*