title: Validation of a leg-to-leg bioimpedance analysis system in assessing body composition in postmenopausal women.
abstract: OBJECTIVE
  To evaluate the validity of a leg-to-leg bioimpedance analysis (BIA) system in predicting body composition as measured by dual-energy X-ray absorptiometry (DXA) in postmenopausal women.
  
  
  METHODS
  Body fat mass (FM), %Fat and fat free mass (FFM) were measured in 124 postmenopausal women (age: 51-63 y, body mass index (BMI): 17-38 kg/m2) first by the leg-to-leg BIA system, and then by DXA as reference method. Bland-Altman analysis was used to determine the bias and 95% limits of agreement between the two methods for the assessment of the individual. Precision error (CV%) of the BIA system was obtained by repeated measurements with intermediate repositioning.
  
  
  RESULTS
  The leg-to-leg BIA system had a high reproducibility with within-day CVs being 0.6% for FFM and 1.1% for FM, and between-day CVs about twice that. The impedance index (Ht2/Z) obtained by the leg-to-leg BIA was moderately correlated to FFM measured by DXA (r=0.66). A significant, systematic bias was observed between the two methods. The BIA system overestimated FM by a mean of 3.1 kg, and underestimated FFM by 2.7 kg. The analysis of 95% limits of agreement showed that for most individuals, %Fat estimated by the BIA might differ from that measured by DXA by 12% below to 45% above, indicating the lack of agreement between the two methods for the assessment of the individual.
  
  
  CONCLUSIONS
  The leg-to-leg BIA system can provide simple, rapid and highly reproducible measurements of body composition for groups, but it has limited accuracy for the assessment of the individual. Population-specific equations will be needed to improve its accuracy in estimating body composition in postmenopausal women.
authors.affiliation: Department of Clinical Physiology, Hilleroed Hospital, DK-3400 Hilleroed, Denmark. xiong@dadlnet.dk
authors.forename: X
authors.initials: X
authors.lastname: Xie
authors.forename: N
authors.initials: N
authors.lastname: Kolthoff
authors.forename: O
authors.initials: O
authors.lastname: Bärenholt
authors.forename: S P
authors.initials: SP
authors.lastname: Nielsen
mesh_terms: D015502:Absorptiometry, Photon; D001823:Body Composition; D015992:Body Mass Index; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007866:Leg; D008875:Middle Aged; D017698:Postmenopause; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity