Estimated lean body mass is more appropriate than body surface area for scaling glomerular filtration rate and extracellular fluid volume.
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.
Peters
A Michael
AM
Department of Nuclear Medicine, Royal Sussex County Hospital, Brighton, UK. a.m.peters@bsms.ac.uk
Snelling
Hayley L R
HL
Glass
Daphne M
DM
Love
Shirley
S
Bird
Nicholas J
NJ
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