The accuracy and precision of DXA for assessing body composition in team sport athletes

This study determined the precision of pencil and fan beam dual-energy X-ray absorptiometry (DXA) devices for assessing body composition in professional Australian Football players. Thirty-six professional Australian Football players, in two groups (fan DXA, N=22; pencil DXA, N=25), underwent two consecutive DXA scans. A whole body phantom with known values for fat mass, bone mineral content and fat-free soft tissue mass was also used to validate each DXA device. Additionally, the criterion phantom was scanned 20 times by each DXA to assess reliability. Test-retest reliability of DXA anthropometric measures were derived from repeated fan and pencil DXA scans. Fat-free soft tissue mass and bone mineral content from both DXA units showed strong correlations with, and trivial differences to, the criterion phantom values. Fat mass from both DXA showed moderate correlations with criterion measures (pencil: r=0.64; fan: r=0.67) and moderate differences with the criterion value. The limits of agreement were similar for both fan beam DXA and pencil beam DXA (fan: fat-free soft tissue mass=-1650 +/- 179g, fat mass=-357 +/- 316g, bone mineral content=289 +/- 122g; pencil: fat-free soft tissue mass=-1701 +/- 257g, fat mass=-359 +/- 326g, bone mineral content=177 +/- 117g). DXA also showed excellent precision for bone mineral content (coefficient of variation (%CV) fan=0.6%; pencil=1.5%) and fat-free soft tissue mass (%CV fan=0.3%; pencil=0.5%) and acceptable reliability for fat measures (%CV fan: fat mass=2.5%, percent body fat=2.5%; pencil: fat mass=5.9%, percent body fat=5.7%). Both DXA provide precise measures of fat-free soft tissue mass and bone mineral content in lean Australian Football players. DXA-derived fat-free soft tissue mass and bone mineral content are suitable for assessing body composition in lean team sport athletes.