Dual energy X-ray absorptiometry (DXA) is an accepted time efficient method of body composition assessment for total body and regional fat mass, lean mass and bone mineral content but for longitudinal monitoring the measurements must be sufficiently reliable. The aim of this study was to compare the reliability of a new positioning protocol (Nana et al) with the current reference (National Health and Nutrition Examination Survey (NHANES)) protocol as well as investigate their within protocol precision.Thirty healthy adults (16 females, 14 males) underwent four whole body DXA scans in succession with full repositioning between scans. The scan order was randomised, with two scans undertaken in accordance with the current NHANES protocol and two using the Nana et al protocol. Magnitudes of typical errors of measurement and changes in the mean of DXA body composition estimates were assessed as standardised effect sizes. The Nana et al protocol repositioning produced trivial typical errors for total body across all lean mass estimates except for fat mass in the arms and trunk which were moderately substantial. The NHANES protocol produced similar typical errors for all measurements in lean mass except for fat mass and bone mineral content in the trunk and arms which were substantially larger than the smallest worthwhile effect. The difference between protocols produced substantially large typical errors in estimations of both total body fat mass and regional fat mass and bone mineral content but differences in lean mass were all less than the smallest worthwhile effect. Although both protocols demonstrated acceptable intra-test reliability the Nana et al protocol produced enhanced precision in regional (arms and trunk) fat mass and bone mineral content. The protocols were substantially different in body composition assessment especially for fat mass and thus should not to be interchanged. Anecdotally, subjects felt more comfortable and supported during the scan with the Nana et al protocol.
2015 University Research Conference: Integrate, Innovate, Inspire, Sunshine Coast, Australia 13-16 July 2015