title: Preoperative and postoperative agreement in fat free mass (FFM) between bioelectrical impedance spectroscopy (BIS) and dual-energy X-ray absorptiometry (DXA) in patients undergoing cardiac surgery.
abstract: OBJECTIVE
  To measure undernutrition in terms of fat free mass (FFM), there are several options. The aim of this study was to assess agreement in FFM between the portable, bedside bioelectrical impedance spectrometry (BIS) and relatively expensive, non-portable dual-energy X-ray absorptiometry (DXA) in patients undergoing cardiac surgery.
  
  
  METHODS
  In a prospective study, body composition measurements by BIS and DXA were performed two weeks prior and two months after cardiac surgery. Preoperative and postoperative agreement in FFM between BIS and DXA were analyzed with Bland and Altman plots.
  
  
  RESULTS
  Twenty-six patients were analyzed. BIS overestimated preoperative and postoperative FFM by 2 kg compared to DXA (2.3 kg (95%CI: -3.5-8.1 kg) and 2.1 kg (95%CI: -4.5-8.7 kg), respectively). BIS underestimated FFM change by -0.5% (95%CI: -8.4-7.5%).
  
  
  CONCLUSIONS
  There is a large inter-individual variation between BIS and DXA. This hinders the interchange-ability of BIS and DXA in routine clinical practice and may lead to misclassifications and thereby inappropriate nutritional treatment and possible postoperative complications. To evaluate nutritional therapy in patients undergoing cardiac surgery, we advocate the use of DXA assessed FFM in parallel to BIS assessed extracellular and intracellular water and FFM.
authors.affiliation: Departments of Dietetics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. l.m.vanvenrooij@amc.uva.nl
authors.forename: Lenny M W
authors.initials: LM
authors.lastname: van Venrooij
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
authors.forename: Rien
authors.initials: R
authors.lastname: de Vos
authors.forename: Mieke M M J
authors.initials: MM
authors.lastname: Borgmeijer-Hoelen
authors.forename: Paul A M
authors.initials: PA
authors.lastname: van Leeuwen
authors.forename: Bas A J M
authors.initials: BA
authors.lastname: de Mol
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000368:Aged; D001823:Body Composition; D004041:Dietary Fats; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D044342:Malnutrition / Q000378:metabolism; D008875:Middle Aged; D009752:Nutritional Status; D011184:Postoperative Period; D057234:Preoperative Period; D011446:Prospective Studies; D013903:Thoracic Surgery
chemical_list: D004041:Dietary Fats