title: The use of bioelectric impedance analysis to measure fluid compartments in subjects with chronic paraplegia.
abstract: OBJECTIVE
  To determine the sensitivity and specificity of body mass index (BMI) as a surrogate marker of obesity in individuals with chronic paraplegia and to validate bioelectric impedance analysis (BIA) as a method of measuring body composition in this group.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Convenience sample of 31 subjects with paraplegia (19 men, 12 women; mean age, 34.2+/-8.8y) and 62 able-bodied control subjects (30 men, 32 women; mean age, 28.6+/-7.2y).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Total-body water (TBW) by deuterium dilution; extracellular water (ECW) by corrected bromide space. Fat-free mass (FFM)=TBW/.732; fat mass (FM)=weight-FFM. Single-frequency whole-body and segmental BIA, and multifrequency whole-body BIA.
  
  
  RESULTS
  BMI had 100% specificity and 20% sensitivity in distinguishing obese from nonobese subjects with paraplegia. TBW was predicted by using the equation: TBW (inL)=2.11-0.1age+3.45sex+.34wt+.28(ht(2)/R)-.086sex x wt(r(2)=.95, standard error of the estimate [SEE]=1.86L, P<.0001). This equation had 81.8% specificity and 68.4% sensitivity. ECW was predicted by using the equation: ECW (in L)=-.025+1.03sex+.187wt+.0041(ht(2)/X(c)) -.033sex x wt (r(2)=.75, SEE=1.62L, P<.0001). Multifrequency BIA offered no greater prediction of TBW or ECW than single-frequency BIA.
  
  
  CONCLUSIONS
  BMI has excellent specificity but poor sensitivity in distinguishing obese from nonobese individuals with paraplegia. TBW (and therefore FFM and FM) and ECW can be reasonably well predicted by using single-frequency BIA.
authors.affiliation: Department of Nutritional Sciences, University of Toronto, ON, Canada.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Buchholz
authors.forename: Colleen F
authors.initials: CF
authors.lastname: McGillivray
authors.forename: Paul B
authors.initials: PB
authors.lastname: Pencharz
mesh_terms: D000328:Adult; D001825:Body Fluid Compartments; D001827:Body Height; D015992:Body Mass Index; D001834:Body Water / Q000378:metabolism; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis* / Q000378:metabolism; D010264:Paraplegia / Q000150:complications* / Q000378:metabolism; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity