title: A bedside measure of body composition in Duchenne muscular dystrophy.
abstract: BACKGROUND
  In clinical practice, monitoring body composition is a critical component of nutritional assessment and weight management in boys with Duchenne muscular dystrophy. We aimed to evaluate the accuracy of a simple bedside measurement tool for body composition, namely bioelectrical impedance analysis, in boys with Duchenne muscular dystrophy.
  
  
  METHODS
  Measures of fat-free mass were determined using a bioelectrical impedance analysis machine and compared against estimations obtained from a reference body composition model. Additionally, the use of raw impedance values was analyzed using three existing predictive equations for the estimation of fat-free mass. Accuracy of bioelectrical impedance analysis was assessed by comparison against the reference model by calculation of biases and limits of agreement.
  
  
  RESULTS
  Body composition was measured in 10 boys with Duchenne muscular dystrophy, mean age 9.01 ± 2.34 years. The bioelectrical impedance analysis machine values of fat-free mass were on average 2.3 ± 14.1 kg higher than reference values. Limits of agreement (based on 95% confidence interval of the mean) were -7.4 to 2.9 kg. There was a significant correlation between the mean fat-free mass and difference in fat-free mass between the bioelectrical impedance analysis machine and the reference model (r = -0.86; P = 0.02) suggesting that the bias was not consistent across the range of measurements. The most accurate predictive equation for the estimation of fat-free mass using raw impedance values was the equation by Pietrobelli et al. (mean difference, -0.7 kg; 95% limits of agreement, -3.5 to 2.0 kg).
  
  
  CONCLUSIONS
  In a clinical setting, where a rapid assessment of body composition is advantageous, the use of raw impedance values, combined with the equation by Pietrobelli et al., is recommended for the accurate estimation of fat-free mass, in boys with Duchenne muscular dystrophy.
authors.affiliation: Children's Nutrition Research Centre, Queensland Children's Medical Research Institute, The University of Queensland, Herston, Queensland, Australia.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Elliott
authors.affiliation: Department of Nutrition and Dietetics, Southern Clinical School, Monash University, Clayton, Victoria, Australia.
authors.forename: Zoe E
authors.initials: ZE
authors.lastname: Davidson
authors.affiliation: Children's Nutrition Research Centre, Queensland Children's Medical Research Institute, The University of Queensland, Herston, Queensland, Australia.
authors.forename: Peter S W
authors.initials: PS
authors.lastname: Davies
authors.affiliation: Department of Nutrition and Dietetics, Southern Clinical School, Monash University, Clayton, Victoria, Australia. Electronic address: helen.truby@monash.edu.
authors.forename: Helen
authors.initials: H
authors.lastname: Truby
mesh_terms: D000886:Anthropometry; D001823:Body Composition; D002648:Child; D017097:Electric Impedance; D006801:Humans; D008297:Male; D008954:Models, Biological; D020388:Muscular Dystrophy, Duchenne / Q000175:diagnosis* / Q000503:physiopathology*
keywords: bioelectrical impedance; body composition; duchenne muscular dystrophy; fat mass; fat-free mass