DXA body composition studies are not affected by extracellular water measurements using stable sodium bromide dilution

Body composition studies using dual energy x-ray absorptiometry (DXA) are b eing increasingly reported in the literature, when DXA body composition mea surements are combined with body water studies, stable bromide is often adm inistered to measure extracellular water. Bromine attenuates x-rays signifi cantly more than soft tissue and so could affect DXA body composition analy sis. DXA scans were performed on 26 adults (12 F, 14 M) before and after the int ravenous injection of 3 g sodium bromide (NaBr). No significant differences were noted pre- and post-NaBr infusion for whole-body fat mass, fat-free s oft-tissue mass and bone mineral content. These findings were supported by a simple mathematical analysis of the like ly effect of the sodium bromide infusion. This showed that when 3 g NaBr wa s introduced into the body, the effect on fat mass estimates was expected t o be marginally less than the precision of the DXA technique.