title: Assessment of EchoMRI-AH versus dual-energy X-ray absorptiometry to measure human body composition.
abstract: BACKGROUND
  The sensitivity to detect small changes in body composition (fat mass and fat-free mass) largely depends on the precision of the instrument. We compared EchoMRI-AH and dual-energy X-ray absorptiometry (DXA) (Hologic QDR-4500A) for estimating fat mass in 301 volunteers.
  
  
  METHODS
  Body composition was evaluated in 136 males and 165 females with a large range of body mass index (BMI) (19-49 kg m(-2)) and age (19-91 years old) using DXA and EchoMRI-AH. In a subsample of 13 lean (BMI=19-25 kg m(-2)) and 21 overweight/obese (BMI>25 kg m(-2)) individuals, within-subject precision was evaluated from repeated measurements taken within 1 h (n=3) and 1 week apart (mean of three measurements taken on each day).
  
  
  RESULTS
  Using Bland-Altman analysis, we compared the mean of the fat mass measurements versus the difference in fat mass measured by both instruments. We found that EchoMRI-AH quantified larger amount of fat versus DXA in non-obese (BMI<30 kg m(-2) (1.1 kg, 95% confidence interval (CI(95)):-3.7 to 6.0)) and obese (BMI ≥ 30 kg m(-2) (4.2 kg, CI(95):-1.4 to 9.8)) participants. Within-subject precision (coefficient of variation, %) in fat mass measured within 1 h was remarkably better when measured by EchoMRI-AH than DXA (<0.5 versus <1.5%, respectively; P<0.001). However, 1-week apart within-subject variability showed similar values for both instruments (<2.2%; P=0.15).
  
  
  CONCLUSIONS
  EchoMRI-AH yielded greater fat mass values when compared with DXA (Hologic QDR-4500A), particularly in fatter subjects. EchoMRI-AH and DXA showed similar 1-week apart precision when fat mass was measured both in lean and overweight/obese individuals.
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Galgani
authors.forename: S R
authors.initials: SR
authors.lastname: Smith
authors.forename: E
authors.initials: E
authors.lastname: Ravussin
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D050218:Body Fat Distribution; D015992:Body Mass Index; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D051598:Whole Body Imaging; D055815:Young Adult