title: Cross-calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry for the assessment of total and appendicular body composition in healthy subjects aged 21-82 years.
abstract: OBJECTIVE
  To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults.
  
  
  METHODS
  A cross-sectional study was carried out.
  
  
  METHODS
  Sixty-eight females and 42 males aged 21-82 years participated in the study.
  
  
  METHODS
  Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs.
  
  
  RESULTS
  The resistance index (RI), i.e. the height(2)/resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM (vs 0.57), 45% more variance of LTM(arm) (vs 0.48) and 36% more variance of LTM(leg) (vs 0.50) (p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI x sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM(arm) and LTM(leg).
  
  
  CONCLUSIONS
  Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.
authors.affiliation: Department of Hygiene, Microbiology and Biostatistics, Faculty of Medicine and Surgery, University of Modena and Reggio Emilia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Malavolti
authors.forename: C
authors.initials: C
authors.lastname: Mussi
authors.forename: M
authors.initials: M
authors.lastname: Poli
authors.forename: A L
authors.initials: AL
authors.lastname: Fantuzzi
authors.forename: G
authors.initials: G
authors.lastname: Salvioli
authors.forename: N
authors.initials: N
authors.lastname: Battistini
authors.forename: G
authors.initials: G
authors.lastname: Bedogni
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001132:Arm / Q000033:anatomy & histology*; D001823:Body Composition / Q000502:physiology*; D002138:Calibration; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007866:Leg / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012727:Sex Characteristics; D013909:Thorax / Q000033:anatomy & histology*