title: New bioimpedance analysis system: improved phenotyping with whole-body analysis.
abstract: OBJECTIVE
  Bioimpedance analysis (BIA) is a potential field and clinical method for evaluating skeletal muscle mass (SM) and %fat. A new BIA system has 8-(two on each hand and foot) rather than 4-contact electrodes allowing for rapid 'whole-body' and regional body composition evaluation.
  
  
  METHODS
  This study evaluated the 50 kHz BC-418 8-contact electrode and TBF-310 4-contact electrode foot-foot BIA systems (Tanita Corp., Tokyo, Japan).
  
  
  METHODS
  There were 40 subject evaluations in males (n=20) and females (n=20) ranging in age from 6 to 64 y. BIA was evaluated in each subject and compared to reference lean soft-tissue (LST) and %fat estimates in the appendages and remainder (trunk+head) provided by dual-energy X-ray absorptiometry (DXA). Appendicular LST (ALST) estimates from both BIA and DXA were used to derive total body SM mass.
  
  
  RESULTS
  The highest correlation between total body LST by DXA and impedance index (Ht(2)/Z) by BC-418 was for the foot-hand segments (r=0.986; left side only) compared to the arm (r=0.970-0.979) and leg segments (r=0.942-0.957)(all P<0.001). The within- and between-day coefficient of variation for %fat and ALST evaluated in five subjects was <1% and approximately 1-3.7%, respectively. The correlations between 8-electrode predicted and DXA appendicular (arms, legs, total) and trunk+head LST were strong and highly significant (all r> or =0.95, P<0.001) and group means did not differ across methods. Skeletal muscle mass calculated (Kim equation) from total ALST by DXA (X+/-s.d.)(23.7+/-9.7 kg) was not significantly different and highly correlated with BC-418 estimates (25.2+/-9.6 kg; r=0.96, P<0.001). There was a good correlation between total body %fat by 8-electrode BIA vs DXA (r=0.87, P<0.001) that exceeded the corresponding association with 4-electrode BIA (r=0.82, P<0.001). Group mean segmental %fat estimates from BC-418 did not differ significantly from corresponding DXA estimates. No between-method bias was detected in the whole body, ALST, and skeletal muscle analyses.
  
  
  CONCLUSIONS
  The new 8-electrode BIA system offers an important new opportunity of evaluating SM in research and clinical settings. The additional electrodes of the new BIA system also improve the association with DXA %fat estimates over those provided by the conventional foot-foot BIA.
authors.affiliation: Pediatric Unit, Verona University Medical School, Verona, Italy. angpie@tin.it
authors.forename: A
authors.initials: A
authors.lastname: Pietrobelli
authors.forename: F
authors.initials: F
authors.lastname: Rubiano
authors.forename: M-P
authors.initials: MP
authors.lastname: St-Onge
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D002648:Child; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011237:Predictive Value of Tests