title: Development and validation of bioelectrical impedance analysis equations for predicting total body water and fat-free mass in North-African adults.
abstract: OBJECTIVE
  Accuracy of the bioelectrical impedance analysis (BIA) depends on population-specific prediction equations. The aim of our study was to develop prediction equations for assessing total body water (TBW) and fat-free mass (FFM) in healthy North-African adults.
  
  
  METHODS
  In all, 250 participants (194 women, 56 men) aged 18-64 years were included in the analysis. BIA variables were measured by a tetra-polar device. TBW and FFM were assessed by the dilution of deuterium (D2O). The participants were sorted by gender and randomly split into development and validation subgroups. The validity of other published equations was also tested using Bland and Altman procedure, proportional bias and pure error.
  
  
  RESULTS
  The prediction equations derived were: TBW (l)=5.68+0.267 height(2)/resistance+4.42 sex (male=1, female=0) + 0.225 weight-0.052 age (R(2)=0.92, root mean square error (RMSE)=1.75 l, RMSE%=5.65); and FFM (kg)=7.47 + 0.366 height(2)/resistance+6.04 sex + 0.306 weight-0.063 age (R(2)=0.92, RMSE=2.38 kg, RMSE%=5.61). The new equations provided nonsignificant proportional bias values, and better agreement than other tested equations. Bias and pure error values were 0.36 and 1.88 l for men and 0.00 and 1.82 l for women, for TBW equation. For FFM equation, bias values were 0.43 and -0.04 kg, and pure errors were 2.57 and 2.46  kg for men and women, respectively.
  
  
  CONCLUSIONS
  The new prediction equations provide reliable estimates of TBW and FFM in North-African adults and are recommended for use in these populations.
authors.affiliation: Joint Unit of Research in Nutrition and Food Sciences, Ibn Tofail University-CNESTEN, Rabat, Morocco.
authors.forename: K E
authors.initials: KE
authors.lastname: Aglago
authors.forename: I El
authors.initials: IE
authors.lastname: Menchawy
authors.forename: K El
authors.initials: KE
authors.lastname: Kari
authors.forename: A El
authors.initials: AE
authors.lastname: Hamdouchi
authors.forename: A
authors.initials: A
authors.lastname: Barkat
authors.forename: R
authors.initials: R
authors.lastname: Bengueddour
authors.forename: N El
authors.initials: NE
authors.lastname: Haloui
authors.forename: N
authors.initials: N
authors.lastname: Mokhtar
authors.forename: H
authors.initials: H
authors.lastname: Aguenaou
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D000352:Africa, Northern; D018912:Arabs; D044383:Black People; D001823:Body Composition; D001825:Body Fluid Compartments; D015992:Body Mass Index; D001834:Body Water; D003903:Deuterium; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques; D008297:Male; D055641:Mathematical Concepts; D009765:Obesity / Q000208:ethnology; D015203:Reproducibility of Results; D012737:Sex Factors
chemical_list: D003903:Deuterium