title: A multi-center comparison of dual energy X-ray absorptiometers: in vivo and in vitro soft tissue measurement.
abstract: OBJECTIVE
  To assess intra- and inter-site soft tissue variability by dual energy X-ray absorptiometry (DXA).
  
  
  METHODS
  Cross-sectional trial.
  
  
  METHODS
  Three medical research institutions.
  
  
  METHODS
  Five humans (in vivo) and four phantoms (in vitro), configured from two whole body phantoms with artificial skeletons and thickness overlays.
  
  
  METHODS
  Duplicate total-body DXA scans were performed on all subjects at each institution within a 15 d period.
  
  
  RESULTS
  All intra-site coefficients of variation (CV) were < 0.5% for total tissue mass, but in vitro and in vivo Cvs were 7.2% and 2.3% for fat mass (FM) and 2.5% and 0.9% for lean mass (LM), respectively. Several total-body and regional FM and LM measurements were significantly different between sites (P < 0.05), with percent differences between sites ranging from 2.6-13.3% for FM and from 1.6-13.6% for LM. Site 2 was consistently lower for FM and Site 3 was consistently lower for LM.
  
  
  CONCLUSIONS
  These results stress the need for both rigorous and standardized cross-calibration procedures for soft tissue measurement by DXA.
authors.affiliation: Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Economos
authors.forename: M E
authors.initials: ME
authors.lastname: Nelson
authors.forename: M A
authors.initials: MA
authors.lastname: Fiatarone
authors.forename: G E
authors.initials: GE
authors.lastname: Dallal
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: S
authors.initials: S
authors.lastname: Yasumara
authors.forename: R
authors.initials: R
authors.lastname: Ma
authors.forename: A N
authors.initials: AN
authors.lastname: Vaswani
authors.forename: M
authors.initials: M
authors.lastname: Russell-Aulet
authors.forename: R N
authors.initials: RN
authors.lastname: Pierson
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D000328:Adult; D001823:Body Composition; D001835:Body Weight; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged