title: Quantifying acute changes in volume and nutritional status during haemodialysis using bioimpedance analysis.
abstract: OBJECTIVE
  To determine the precision of multi-frequency bioimpedance analysis (MFBIA) in quantifying acute changes in volume and nutritional status during haemodialysis, in patients with end-stage renal disease (ESRD).
  
  
  METHODS
  Using whole-body MFBIA, we prospectively studied changes in total body water (TBW), extracellular volume (ECV), intracellular volume (ICV), lean body mass (LBM), body cell mass (BCM) and fat mass (FM), pre- and post-haemodialysis and tested the agreement of volume changes with corresponding acute weight change and ultrafiltration volume (UF) using Bland-Altman analysis.
  
  
  RESULTS
  Forty-four prevalent and 17 incident haemodialysis patients were studied (median age 55 years, 56% males). MFBIA-derived TBW, ECV, ICV, LBM and BCM were significantly reduced after haemodialysis (P < 0.001), but FM remained constant. TBW change estimated weight change with mean bias of -0.52 L, with 56/61 (91.8%) data points within limits of agreement (-2.74 L, 1.69 L). TBW change estimated UF with mean bias of -0.62 L, with 55/61 (90.2%) data points within limits of agreement (-2.68 L, 1.43 L). ECV change underestimated weight change and UF with mean bias of -1.17 L and -1.27 L respectively. Similarly, ICV change underestimated both clinical measures with corresponding mean bias of -1.34 L and -1.44 L. Comparing incidents versus prevalent haemodialysis patients, TBW change estimated weight change with smaller mean bias (-0.10 L vs-0.69 L, respectively) and narrower limits of agreement.
  
  
  CONCLUSIONS
  Multi-frequency bioimpedance analysis-derived TBW chan e has the best agreement with acute clinical volume change during haemodialysis compared to ECV or ICV change alone, but overall degree of precision remains poor. Nutritional assessment using LBM and BCM measurements is significantly confounded by hydration status.
authors.affiliation: Division of Nephrology, University Medicine Cluster, National University Hospital, Singapore. horng.ruey.chua@gmail.com
authors.forename: Horng-Ruey
authors.initials: HR
authors.lastname: Chua
authors.forename: Ling
authors.initials: L
authors.lastname: Xiang
authors.forename: Pek-Yee
authors.initials: PY
authors.lastname: Chow
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Liang
authors.initials: L
authors.lastname: Shen
authors.forename: Evan
authors.initials: E
authors.lastname: Lee
authors.forename: Boon-Wee
authors.initials: BW
authors.lastname: Teo
mesh_terms: D050154:Adiposity; D001834:Body Water / Q000378:metabolism*; D001835:Body Weight; D017097:Electric Impedance; D045604:Extracellular Fluid / Q000378:metabolism*; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism*; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D015596:Nutrition Assessment; D009752:Nutritional Status; D011446:Prospective Studies; D006435:Renal Dialysis; D014882:Water-Electrolyte Balance