Estimation of thigh muscle cross-sectional area by dual-energy X-ray absorptiometry in frail elderly patients.
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.
Hansen
Ross D
RD
Gastrointestinal Investigation Unit, Royal North Shore Hospital, St Leonards, NSW, Australia. hansenr@med.usyd.edu.au
Williamson
Dominique A
DA
Finnegan
Terence P
TP
Lloyd
Brad D
BD
Grady
Jodie N
JN
Diamond
Terrence H
TH
Smith
Emma Ur
EU
Stavrinos
Theodora M
TM
Thompson
Martin W
MW
Gwinn
Tom H
TH
Allen
Barry J
BJ
Smerdely
Peter I
PI
Diwan
Ashish D
AD
Singh
Nalin A
NA
Singh
Maria A Fiatarone
MA
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