title: Estimation of thigh muscle cross-sectional area by dual-energy X-ray absorptiometry in frail elderly patients.
abstract: BACKGROUND
  Thigh muscle mass and cross-sectional area (CSA) are useful indexes of sarcopenia and the response to treatment in older patients. Current criterion methods are computed tomography (CT) and magnetic resonance imaging.
  
  
  OBJECTIVE
  The objective was to compare thigh muscle mass estimated by dual-energy X-ray absorptiometry (DXA), a less expensive and more accessible method, with thigh muscle CSA determined by CT in a group of elderly patients recovering from hip fracture.
  
  
  METHODS
  Midthigh muscle CSA (in cm(2)) was assessed from a 1-mm CT slice and midthigh muscle mass (g) from a 1.3-cm DXA slice in 30 patients (24 women) aged 81 +/- 8 y during 12 mo of follow-up. Fat-to-lean soft tissue ratios were calculated with each technique to permit direct comparison of a variable in the same units.
  
  
  RESULTS
  Baseline midthigh muscle CSA was highly correlated with midthigh muscle mass (r = 0.86, P < 0.001) such that DXA predicted CT-determined CSA with an SEE of 10 cm(2) (an error of approximately 12% of the mean CSA value). CT- and DXA-determined ratios of midthigh fat to lean mass were similarly related (intraclass correlation coefficient = 0.87, P < 0.001). When data were expressed as the changes from baseline to follow-up, CT and DXA changes were weakly correlated (intraclass correlation coefficient = 0.51, P = 0.019).
  
  
  CONCLUSIONS
  Assessment of sarcopenia by DXA midthigh slice is a potential low-radiation, accessible alternative to CT scanning of older patients. The errors inherent in this technique indicate, however, that it should be applied to groups of patients rather than to individuals or to evaluate the response to interventions.
authors.affiliation: Gastrointestinal Investigation Unit, Royal North Shore Hospital, St Leonards, NSW, Australia. hansenr@med.usyd.edu.au
authors.forename: Ross D
authors.initials: RD
authors.lastname: Hansen
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Williamson
authors.forename: Terence P
authors.initials: TP
authors.lastname: Finnegan
authors.forename: Brad D
authors.initials: BD
authors.lastname: Lloyd
authors.forename: Jodie N
authors.initials: JN
authors.lastname: Grady
authors.forename: Terrence H
authors.initials: TH
authors.lastname: Diamond
authors.forename: Emma Ur
authors.initials: EU
authors.lastname: Smith
authors.forename: Theodora M
authors.initials: TM
authors.lastname: Stavrinos
authors.forename: Martin W
authors.initials: MW
authors.lastname: Thompson
authors.forename: Tom H
authors.initials: TH
authors.lastname: Gwinn
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Allen
authors.forename: Peter I
authors.initials: PI
authors.lastname: Smerdely
authors.forename: Ashish D
authors.initials: AD
authors.lastname: Diwan
authors.forename: Nalin A
authors.initials: NA
authors.lastname: Singh
authors.forename: Maria A Fiatarone
authors.initials: MA
authors.lastname: Singh
mesh_terms: D015502:Absorptiometry, Photon / Q000191:economics / Q000379:methods* / Q000592:standards; D000369:Aged, 80 and over; D000375:Aging; D005260:Female; D016330:Frail Elderly; D015577:Geriatric Assessment; D006620:Hip Fractures / Q000601:surgery; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D009133:Muscular Atrophy / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013848:Thigh; D014057:Tomography, X-Ray Computed / Q000191:economics / Q000379:methods / Q000592:standards