title: Four-compartment cellular level body composition model: comparison of two approaches.
abstract: OBJECTIVE
  The aim of this study was to develop and compare two DXA-based four-compartment [body weight=body cell mass (BCM)+extracellular fluid (ECF)+extracellular solids (ECS)+fat] cellular level models.
  
  
  METHODS
  Total body potassium (TBK) model: BCM from TBK by whole-body counting-ECF(TBK)=LST-[BCM(TBK)+0.73 x osseous mineral (Mo)]. Bromide model: ECF from sodium bromide dilution-BCM(BROMIDE)=LST-(ECF(BROMIDE)+0.73xMo); Mo and LST measurements came from DXA. The two approaches were evaluated in 99 healthy men and 118 women.
  
  
  RESULTS
  BCM estimates were highly correlated (r=0.97, p<0.001), as were ECF estimates (r=0.87, p<0.001); a small statistically significant mean difference was present (mean+/-SD; BCM(TBK) model, 30.4+/-8.9 kg; BCM(BROMIDE), 31.4+/-9.3 kg; Delta=1.0+/-2.8 kg; p<0.001; ECF(TBK), 18.5+/-4.2 kg; ECF(BROMIDE), 17.5+/-3.6 kg; Delta=1.0+/-2.8 kg; p<0.001). A high correlation (r=0.97, p<0.001) and good agreement (38.9+/-9.5 vs. 38.9+/-9.5 kg; Delta=0.0+/-2.4 kg; p=0.39) were present between TBW, derived as the sum of intracellular water from TBK and ECW from bromide, and measured TBW by 2H2O dilution.
  
  
  CONCLUSIONS
  Two developed four-compartment cellular level DXA models, one of which is appropriate for use in most clinical and research settings, provide comparable results and are applicable for BCM and ECF estimation of subject groups with hydration disturbances.
authors.affiliation: Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons and Institute of Human Nutrition, Weight Control Unit, 1090 Amsterdam Avenue, 14th Floor, New York, NY 10025, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: St-Onge
authors.forename: Angelo
authors.initials: A
authors.lastname: Pietrobelli
authors.forename: Jack
authors.initials: J
authors.lastname: Wang
authors.forename: ZiMian
authors.initials: Z
authors.lastname: Wang
authors.forename: Stanley
authors.initials: S
authors.lastname: Heshka
authors.forename: Steven B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D001965:Bromides / Q000032:analysis; D045604:Extracellular Fluid / Q000502:physiology; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques; D008297:Male; D008954:Models, Biological; D011197:Potassium Radioisotopes / Q000032:analysis; D017670:Sodium Compounds / Q000032:analysis; D014915:Whole-Body Counting
chemical_list: D001965:Bromides; D011197:Potassium Radioisotopes; D017670:Sodium Compounds; C027938:sodium bromide