title: Estimation of total-body and limb muscle mass in hemodialysis patients by using multifrequency bioimpedance spectroscopy.
abstract: BACKGROUND
  Skeletal muscle mass can be measured noninvasively with magnetic resonance imaging (MRI), but this is time-consuming and expensive.
  
  
  OBJECTIVE
  We evaluated the use of multifrequency bioimpedance spectroscopy (BIS) measurements of intracellular volume (ICV) to model total-body skeletal muscle mass (TBMM) and limb skeletal muscle mass in hemodialysis patients.
  
  
  METHODS
  TBMM was measured by MRI in 20 male and 18 female hemodialysis patients with a median (range) age of 54 y (33-73 y), weight of 78.9 kg (43.2-120 kg), and body mass index (BMI; in kg/m2) of 27.3 (19.4-46.6). We measured total body water (TBW) by using D2O dilution, extracellular volume (ECV) as bromide space, and ICV as TBW minus bromide space. Total body potassium (TBK) measured as 40K was used as an independent model of TBMM. BIS was used to measure whole-body TBW (ankle to wrist) and TBW in the arms and legs. BIS-estimated ICV was used to construct models to calculate limb muscle mass and TBMM. The latter was compared with models derived from isotopic methods.
  
  
  RESULTS
  BIS yielded a model for TBMM [TBMM = 9.52 + 0.331 x ICV + 2.77 (male) + 0.180 x weight (kg) - 0.133 x age] (R2 = 0.937, P < 0.0001) as precise as TBK-measured TBMM [TBMM = 1.29 + 0.00453 x TBK (mEq) + 1.46 (male) + 0.144 x weight (kg) - 0.0565 x age] (R2 = 0.930, P < 0.0001) or isotopic methods. BIS models were also developed for measuring leg and arm muscle mass.
  
  
  CONCLUSIONS
  BIS provides an estimate of TBMM that correlates well with isotopic methods in approximating values obtained by MRI and can be used to estimate limb muscle mass.
authors.affiliation: Renal Research Institute, New York, NY, USA. gakaysen@ucdavis.edu
authors.forename: George A
authors.initials: GA
authors.lastname: Kaysen
authors.forename: Fansan
authors.initials: F
authors.lastname: Zhu
authors.forename: Shubho
authors.initials: S
authors.lastname: Sarkar
authors.forename: Steven B
authors.initials: SB
authors.lastname: Heymsfield
authors.forename: Jack
authors.initials: J
authors.lastname: Wong
authors.forename: Charoen
authors.initials: C
authors.lastname: Kaitwatcharachai
authors.forename: Martin K
authors.initials: MK
authors.lastname: Kuhlmann
authors.forename: Nathan W
authors.initials: NW
authors.lastname: Levin
mesh_terms: D000328:Adult; D000368:Aged; D001834:Body Water / Q000378:metabolism*; D017666:Deuterium Oxide; D017097:Electric Impedance; D045604:Extracellular Fluid / Q000378:metabolism; D005121:Extremities / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000378:metabolism; D011197:Potassium Radioisotopes; D011237:Predictive Value of Tests; D011865:Radioisotope Dilution Technique; D006435:Renal Dialysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D011197:Potassium Radioisotopes; D017666:Deuterium Oxide