Purpose: Dual energy X-ray absorptiometry (DXA) and air displacement plethysmography (ADP) are commonly used to assess body composition. Accurate body fat measures are valuable in a variety of populations. Because DXA, the reference standard, is expensive and labour-intensive, determining whether these two methods are interchangeable is important.
Methods: Forty-five female undergraduate students aged 21 to 33 with body mass indexes of 18.3 to 28.6 kg/m² were recruited from the University of Guelph. Each participant underwent one full-body DXA scan and one ADP assessment, to determine total percent fat mass (%FM).
Results: The Pearson's correlation between %FM(DXA) (27.1 ± 4.8) and %FM(ADP) (26.1 ± 5.5) indicated good association (r=0.88, p<0.01). While Bland-Altman analysis revealed no systematic bias between the two methods (R2=0.07, p=0.08), large intraindividual variation occurred (95% confidence interval: -5.86% to 4.11%); this was related to height, weight, body-surface area, and lung volume.
Conclusions: The two methods were significantly correlated. Mean %FM was not significantly different and no systematic bias between methods was observed. These findings indicate that ADP and DXA may be used interchangeably for determining %FM at the group level in healthy young women; a large intraindividual variation between the methods precludes interchangeability at the individual level.