Validity of fan-beam dual-energy X-ray absorptiometry for measuring fat-free mass and leg muscle mass

1 Epidemiology, Demography and Biometry Program, National Institute on Aging, Bethesda, Maryland 20892; 2 Institute for Research in Extramural Medicine, Faculty of Medicine, Vrije Universiteit, 1081 BT Amsterdam, The Netherlands; 3 Department of Radiology, University of California, San Francisco, California 94105; and 4 Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 The aim of the study was to examine the accuracy of fan-beam dual-energy X-ray absorptiometry (DEXA) for measuring total body fat-free mass (FFM) and leg muscle mass (MM) in elderly persons. Participants were 60 men and women aged 70-79 yr and with a body mass index of 17.5-39.8 kg/m 2 . FFM and MM at four leg regions were measured by using DEXA (Hologic 4500A, v8.21). A four-compartment body composition model (4C) and multislice computed tomography (CT) of the legs were used as the criterion methods for FFM and MM, respectively. FFM by DEXA was positively associated with FFM by 4C ( R 2 = 0.98, SE of estimate = 1.6 kg). FFM by DEXA was higher [53.5 ± 12.0 (SD) kg] than FFM by 4C (51.6 ± 11.9 kg; P