title: Estimated lean body mass is more appropriate than body surface area for scaling glomerular filtration rate and extracellular fluid volume.
abstract: OBJECTIVE
  To compare body surface area (BSA) with lean body mass (LBM) for scaling extracellular fluid volume (ECV) and glomerular filtration rate (GFR).
  
  
  METHODS
  Phase 1: Total body water (TBW), bromide space and LBM were measured with (3)H-water, (77)Br and dual X-ray absorptiometry, respectively, in 6 healthy adults. Phase 2: ECV and GFR were measured with (51)Cr-EDTA in 95 healthy adults and 56 children (0.5-13 years). ECV was calculated as GFR divided by GFR/ECV, both corrected for the one-compartment assumption. LBM was estimated (eLBM) in adults from height and weight and in children using a height/weight formula for estimating ECV and a constant derived from a separate adult population relating ECV to eLBM.
  
  
  RESULTS
  Phase 1: LBM and BSA correlated closely with TBW and bromide space. With LBM, the regressions passed through the origin, but with BSA, the intercepts were significantly below zero. Phase 2: GFR/BSA and ECV/BSA were higher in men than women but no difference was recorded in GFR/eLBM, GFR/ECV or ECV/eLBM. ECV showed a linear relation with eLBM and a non-linear relation with BSA. GFR/BSA and ECV/BSA correlated significantly with BSA but neither GFR/eLBM nor ECV/eLBM correlated with eLBM.
  
  
  CONCLUSIONS
  eLBM is preferable to BSA for scaling GFR and ECV.
authors.affiliation: Department of Nuclear Medicine, Royal Sussex County Hospital, Brighton, UK. a.m.peters@bsms.ac.uk
authors.forename: A Michael
authors.initials: AM
authors.lastname: Peters
authors.forename: Hayley L R
authors.initials: HL
authors.lastname: Snelling
authors.forename: Daphne M
authors.initials: DM
authors.lastname: Glass
authors.forename: Shirley
authors.initials: S
authors.lastname: Love
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Bird
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D001826:Body Fluids / Q000502:physiology; D015992:Body Mass Index; D001830:Body Surface Area; D002648:Child; D002675:Child, Preschool; D045604:Extracellular Fluid / Q000502:physiology*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013851:Thinness / Q000503:physiopathology; D055815:Young Adult