title: Influence of fluid status on techniques used to assess body composition in peritoneal dialysis patients.
abstract: OBJECTIVE
  A reliable assessment of nutritional state in peritoneal dialysis (PD) patients is of great importance. Nevertheless, techniques used to assess body composition in patients on PD may be affected by abnormalities in fluid status. The primary aim of the present study was to compare different techniques used to evaluate body composition and to assess the influence of fluid status on the assessment of body composition. The secondary aim was to assess the relevance of handgrip muscle strength in the nutritional evaluation of the patient.
  
  
  METHODS
  In 40 PD patients, dual-energy x-ray absorptiometry (DEXA), multifrequency bioimpedance analysis (MF-BIA), and anthropometry were compared with respect to the evaluation of body composition [fat mass and lean body mass (LBM; by DEXA), and fat-free mass (FFM; by MF-BIA, anthropometry]. The influence of fluid status on the measurement of LBM/FFM by the various techniques was assessed by their relation to left ventricular end-diastolic diameter (LVEDD), assessed by echocardiography, and by estimating the ratio between extracellular water (ECW) and total body water (TBW), assessed by bromide and deuterium dilution, with LBM (DEXA). The relevance of handgrip muscle strength as a nutritional parameter was assessed by its relation to LBM and other nutritional parameters.
  
  
  RESULTS
  Despite highly significant correlations, wide limits of agreement between the various techniques were present with respect to assessment of body composition (expressed as % body weight) and were most pronounced for anthropometry: LBM (DEXA) - FFM (MF-BIA) = 3.4% +/- 12.2%; LBM (DEXA) - FFM (anthropometry) = -5.7% +/- 7.8%; fat mass (DEXA - MF-BIA) = -4.2% +/- 7.9%; fat mass (DEXA - anthropometry) = 2.9% +/- 7.2%. The ratio between ECW and LBM (DEXA) was 0.36 +/- 0.08 L/kg (range 0.25 - 0.67 L/kg), and the ratio between TBW and LBM was 0.75 +/- 0.06 L/kg (range 0.63 - 0.86 L/kg), which shows the variability in hydration state of LBM/FFM between individual patients. LBM/FFM measured by all three techniques was significantly related to LVEDD, suggesting an important influence of hydration state on this parameter. Handgrip muscle strength was significantly related to LBM/FFM, as measured by all three techniques, but not to other nutritional parameters.
  
  
  CONCLUSIONS
  Wide limits of agreement were found between various techniques used to assess body composition in PD patients. The assessment of body composition was strongly influenced by hydration state. The handgrip test is related to body composition, but not to other nutritional parameters.
authors.affiliation: Department of Internal Medicine, University Hospital Maastricht, The Netherlands.
authors.forename: Constantijn J A M
authors.initials: CJ
authors.lastname: Konings
authors.forename: Jeroen P
authors.initials: JP
authors.lastname: Kooman
authors.forename: Marc
authors.initials: M
authors.lastname: Schonck
authors.forename: Bernardus
authors.initials: B
authors.lastname: van Kreel
authors.forename: Guido A K
authors.initials: GA
authors.lastname: Heidendal
authors.forename: Emile C
authors.initials: EC
authors.lastname: Cheriex
authors.forename: Frank M
authors.initials: FM
authors.lastname: van der Sande
authors.forename: Karel M L
authors.initials: KM
authors.lastname: Leunissen
mesh_terms: D000328:Adult; D000368:Aged; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status / Q000502:physiology*; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D011237:Predictive Value of Tests; D051437:Renal Insufficiency / Q000503:physiopathology* / Q000628:therapy*; D015203:Reproducibility of Results; D014883:Water-Electrolyte Imbalance / Q000209:etiology* / Q000503:physiopathology*