title: Obesity increases precision errors in total body dual-energy x-ray absorptiometry measurements.
abstract: Total body (TB) dual-energy X-ray absorptiometry (DXA) is increasingly being used to measure body composition in research and clinical settings. This study investigated the effect of body mass index (BMI) and body fat on precision errors for total and regional TB DXA measurements of bone mineral density, fat tissue, and lean tissue using the GE Lunar Prodigy (GE Healthcare, Bedford, UK). One hundred forty-four women with BMI's ranging from 18.5 to 45.9 kg/m(2) were recruited. Participants had duplicate DXA scans of the TB with repositioning between examinations. Participants were divided into 3 groups based on their BMI, and the root mean square standard deviation and the percentage coefficient of variation were calculated for each group. The root mean square standard deviation (percentage coefficient of variation) for the normal (<25 kg/m²; n = 76), overweight (25-30 kg/m²; n = 36), and obese (>30 kg/m²; n = 32) BMI groups, respectively, were total BMD (g/cm(2)): 0.009 (0.77%), 0.009 (0.69%), 0.011 (0.91%); total fat (g): 545 (2.98%), 486 (1.72%), 677 (1.55%); total lean (g): 551 (1.42%), 540 (1.34%), and 781 (1.68%). These results suggest that serial measurements in obese subjects should be treated with caution because the least significant change may be larger than anticipated.
authors.affiliation: Medical Imaging, University of Exeter, Exeter, UK. Electronic address: K.M.Knapp@exeter.ac.uk.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Knapp
authors.affiliation: Medical Imaging, University of Exeter, Exeter, UK.
authors.forename: Joanne R
authors.initials: JR
authors.lastname: Welsman
authors.affiliation: Medical Imaging, University of Exeter, Exeter, UK.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Hopkins
authors.affiliation: Medical Imaging, University of Exeter, Exeter, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Shallcross
authors.affiliation: Imaging Sciences, Guy's, King's and St Thomas' School of Medicine, King's College London, London, UK.
authors.forename: Ignac
authors.initials: I
authors.lastname: Fogelman
authors.affiliation: Imaging Sciences, Guy's, King's and St Thomas' School of Medicine, King's College London, London, UK.
authors.forename: Glen M
authors.initials: GM
authors.lastname: Blake
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015519:Bone Density; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000000981:diagnostic imaging*; D050177:Overweight / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Bone mineral density; dual-energy X-ray absorptiometry; obesity; precision