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Inappropriate use of dual energy absorptiometry body composition estimation


To the Editor: Bone densitometry by means of dual energy absorptiometry (DXA) has been the gold standard for estimating bone mineral density (BMD) for over 3 decades and is pivotal in the current management of osteoporosis. DXA technology relies on measuring the attenuation of two different x-ray energies that can be used to calculate BMD or, alternatively, soft tissue mass, including fat and lean tissue mass. Over the past few years, there has been increasing use of DXA for estimating fat and lean tissue in body composition. These parameters are widely used in research into diseases that affect body composition (such as HIV, obesity and eating disorders), and increasingly in related clinical settings. While using DXA in this way is beneficial in some patients, there is anecdotal evidence of growing inappropriate use or overuse of DXA body composition estimation in monitoring weight loss or exercise programs, often supplied by non-medical practitioners.

Two problems are worth highlighting. First, a number of body composition scan providers imply that total body BMD, provided automatically with the whole body composition scans, can provide a diagnosis of osteoporosis. This is inconsistent with World Health Organization guidelines of osteoporosis being indicated by a T score for bone density that is 2.5 SD or more below the young adult mean, which applies only to the lumbar spine, proximal femur and mid shaft radius…