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Dual energy X-ray absorptiometry
(DXA, previously DEXA) is a means of measuring bone mineral density (BMD). Two X-ray beams with differing energy levels are aimed at the patient's bones. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption of each beam by bone. Dual energy X-ray absorptiometry is the most widely used and most thoroughly studied bone density measurement technology.
DXA scans are primarily used to evaluate bone mineral density. DXA scans can also be used to measure total body composition and fat content. However, it has been suggested that[by whom?] while very accurately measuring minerals, it does not reliably measure fat content, which was not its original purpose. It is suggested that for total body composition, DXA be used in conjunction with another method (underwater weighing, etc.).
Women at risk of osteoporosis, especially if over the age of 50y should get a DXA scan. 'At risk' includes many different clinical risk factors including: prior fragility fracture, use of glucocorticoids, heavy smoking, excess alcohol intake, rheumatoid arthritis, history of parental hip fracture, chronic renal and liver disease, chronic respiratory disease, long-term use of phenobarbitone or phenytoin, celiac disease, inflammatory bowel disease and other risks. The same clinical risk factors in men over 50y should prompt getting a DXA scan too.
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