title: Comparing single-frequency bioelectrical impedance analysis against deuterium dilution to assess total body water.
abstract: OBJECTIVE
  In this study, we aimed to validate the accuracy of single-frequency bioelectrical impedance analysis (SF-BIA) at 50 kHz to assess total body water (TBW) against the reference technique deuterium dilution (D(2)O) and to explore if the simple clinical parameters extracellular fluid (ECF) composition and body shape explain individual differences between D(2)O and SF-BIA (Diff(BIA-D(2)O)).
  
  
  METHODS
  We assessed TBW with D(2)O and SF-BIA in 26 women and 26 men without known disease or anomalous body shapes. In addition, we measured body shape with anthropometry and ECF composition (osmolality, albumin, glucose, urea, creatinine, sodium and potassium).
  
  
  RESULTS
  On group average, SF-BIA to predict TBW agreed well with D(2)O (SF-BIA, 39.8 ± 10.1 l; D(2)O, 40.4 ± 10.2 l; and Diff(BIA-D(2)O) -0.7 l). In four individuals ('outliers'; 15% of the study population), Diff(BIA-D(2)O) was high (-6.8 to +3.8 l). Diff(BIA-D(2)O) was associated with individual variations in body shape rather than ECF composition. Using gender-specific analysis, we found that individual variability of waist circumference in men and arm length in women significantly contributed to Diff(BIA-D(2)O). When removing the four 'outliers', these associations were lost.
  
  
  CONCLUSIONS
  In the majority of our sample, BIA agreed well with D(2)O. Adjusting for individual variability in body shape by anthropometrical assessment could possibly improve the accuracy of SF-BIA for individuals who deviate from mean values with respect to body shape. However, further studies with higher subject numbers are needed to confirm our findings.
authors.affiliation: Experimental and Clinical Research Center, a joint cooperation between Charité Universitätsmedizin and Max-Delbrück Center for Molecular Medicine, Charité Universitätsmedizin, Berlin, Germany. verena.haas@charite.de
authors.forename: V
authors.initials: V
authors.lastname: Haas
authors.forename: T
authors.initials: T
authors.lastname: Schütz
authors.forename: S
authors.initials: S
authors.lastname: Engeli
authors.forename: C
authors.initials: C
authors.lastname: Schröder
authors.forename: K
authors.initials: K
authors.lastname: Westerterp
authors.forename: M
authors.initials: M
authors.lastname: Boschmann
mesh_terms: D000328:Adult; D000886:Anthropometry; D001823:Body Composition; D001834:Body Water / Q000737:chemistry* / Q000378:metabolism; D017666:Deuterium Oxide / Q000737:chemistry / Q000378:metabolism; D017097:Electric Impedance; D045604:Extracellular Fluid / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D011865:Radioisotope Dilution Technique
chemical_list: D017666:Deuterium Oxide