A multi-center comparison of dual energy X-ray absorptiometers: In vivo and in vitro soft tissue measurement

Abstract

Objective: To assess intra- and inter-site soft tissue variability by dual energy X-ray absorptiometry (DXA). Design: Cross-sectional trial. Setting: Three medical research institutions. Subjects: Five humans (in vivo) and four phantoms (in vitro), configured from two whole body phantoms with artificial skeletons and thickness overlays. Interventions: Duplicate total-body DXA scans were performed on all subjects at each institution within a 15 d period. Results: All intra-site coefficients of variation (CV) were <0.5% for total tissue mass, but in vitro and in vivo Cvs were 7.2% and 2.3% for fat mass (FM) and 2.5% and 0.9% for lean mass (LM), respectively. Several total-body and regional FM and LM measurements were significantly different between sites (P < 0.05), with percent differences between sites ranging from 2.6–13.3% for FM and from 1.6–13.6% for LM. Site 2 was consistently lower for FM and Site 3 was consistently lower for LM. Conclusions: These results stress the need for both rigorous and standardized cross-calibration procedures for soft tissue measurement by DXA. Sponsorship: This work has been supported in part by NIH Training Grant #T32AG00209, grant P01-DK42618 from the National Institutes of Health, federal funds from the US Department of Agriculture, and Agricultural Research Services contract 53-3K06-5-10. Dr Nelson is currently a Brookdale National Fellow.