Assessing body composition in taller or broader individuals using dual-energy X-ray absorptiometry: a systematic review.
OBJECTIVE
Dual-energy X-ray absorptiometry (DXA) is an accurate and reliable method for determining body composition, but a limiting feature is the restricted scanning areas (∼190 × 60 cm(2)). This shortcoming is relevant not only to athletes involved in sports where height is a major performance determinant but also to obese individuals with a large trunk mass and breadth in whom body dimensions frequently exceed the scan area. This study reviews solutions for DXA length and/or width limitations and its accuracy for body composition assessment using the PRISMA statement guidelines.


METHODS
Reviewed studies included English language articles from MEDLINE and Thomson Reuters Web of Knowledge platform (1990-2013), and were selected if procedures to overcome the scan area limitations and its validity in assessing the body composition of healthy participants were addressed. Search terms included: DXA, scan, height, width, length, wide, large, tall and obese.


RESULTS
A total of seven studies met the criteria and were selected. The sum of two DXA scans and adopting a knee-bent position are alternative procedures proposed for evaluating individuals using pencil and fan-beam Hologic instruments, who are taller than the scan area, whereas a half-body scan is recommended for overcoming the limitations of whole-body measurements in subjects who are wider than the scan area width of Lunar densitometers.


CONCLUSIONS
Overall, the proposed procedures are useful and valid, in particular the half-body scan alternative, which avoids unnecessary radiation exposure and scanning time. However, these alternatives were developed for specific densitometers, models and scan mode, and applicability to other instruments requires further research.
Exercise and Health Laboratory, CIPER, Fac Motricidade Humana, Univ Tecn Lisboa, Cruz-Quebrada, Portugal.
A M
AM
Silva
S B
SB
Heymsfield
L B
LB
Sardinha
D015502:Absorptiometry, Photon / Q000379:methods*; D001823:Body Composition; D001827:Body Height; D049628:Body Size; D006801:Humans; D009765:Obesity