title: Underweight patients with anorexia nervosa: comparison of bioelectrical impedance analysis using five equations to dual X-ray absorptiometry.
abstract: OBJECTIVE
  Body weight changes do not reflect the respective changes of body compartments, namely fat-free mass (FFM) and fat mass (FM). Both bioelectrical Impedance Analysis (BIA) and the Dual X-ray absorptiometry (DXA) measure FFM and FM. This study in underweight patients with anorexia nervosa (AN) aims to compare measurements of FM and FFM done by DXA and BIA using 5 different BIA equations already validated in healthy population and to identify the most suitable BIA equation for AN patients.
  
  
  METHODS
  Fifty female patients with AN (BMI=14.3 ± 1.49, age=19.98 ± 5.68yrs) were included in the study. Body composition was measured by DXA (Delphi W, Hologic, Bedford, MA) and by 50 kHz BIA (FORANA, Helios) using 5 different BIA equations validated in healthy population (Sun, Geneva, Kushner, Deurenberg and Roubenoff equations). Comparison between the DXA and the 5 BIA equations was done using the sum of the squares of differences and Bland-Altman plots.
  
  
  RESULTS
  The Deurenberg equation gave the best estimates of FFM when compared to the measurements by DXA (FFM(dxa)=35.80 kg versus FFM(deurenberg)=36.36 kg) and very close estimates of FM (FM(dxa)=9.16 kg and FM(deurenberg)=9.57 kg) The Kushner equation showed slightly better estimates for FM (FM(kushner)=9. 0kg) when compared to the DXA, but not for FFM. Sun equation gave the broadest differences for FM and FFM when compared with DXA.
  
  
  CONCLUSIONS
  The best available BIA equation to calculate the FFM and the FM in patients with AN is the Deurenberg equation. It takes into account the weight, height and age and is applicable in adults and adolescents AN patients with BMI of 12.8-21.0, and for ages between 13.4 and up to 36.9 years.
authors.affiliation: INSERM U669, PSIGIAM 'Paris Sud Innovation Group in Adolescent Mental Health', Maison des Adolescents, 97 Boulevard De Port Royal, 75014 Paris, France. lamamattar@gmail.com
authors.forename: Lama
authors.initials: L
authors.lastname: Mattar
authors.forename: Nathalie
authors.initials: N
authors.lastname: Godart
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Melchior
authors.forename: Bruno
authors.initials: B
authors.lastname: Falissard
authors.forename: Sami
authors.initials: S
authors.lastname: Kolta
authors.forename: Damien
authors.initials: D
authors.lastname: Ringuenet
authors.forename: Christine
authors.initials: C
authors.lastname: Vindreau
authors.forename: Clementine
authors.initials: C
authors.lastname: Nordon
authors.forename: Corinne
authors.initials: C
authors.lastname: Blanchet
authors.forename: Claude
authors.initials: C
authors.lastname: Pichard
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000273:Adipose Tissue / Q000502:physiology; D000856:Anorexia Nervosa / Q000503:physiopathology*; D001823:Body Composition / Q000502:physiology; D017097:Electric Impedance; D005260:Female; D006801:Humans; D016014:Linear Models; D013851:Thinness / Q000503:physiopathology*; D055815:Young Adult