Dual-energy X-ray absorptiometry
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| OPS-301 code | 3-900 |
Dual-energy X-ray absorptiometry (DXA, previously DEXA) is a means of measuring bone mineral density (BMD). Two X-ray beams, with different 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.
The DXA scan is typically used to diagnose and follow osteoporosis, as contrasted to the nuclear bone scan, which is sensitive to certain metabolic diseases of bones in which bones are attempting to heal from infections, fractures, or tumors.
DXA scans are used primarily to evaluate bone mineral density. DXA scans can also be used to measure total body composition and fat content with a high degree of accuracy comparable to hydrostatic weighing with a few important caveats. However, it has been suggested that, while very accurately measuring minerals and lean soft tissue (LST), DXA may provide skewed results due to its method of indirectly calculating fat mass by subtracting it from the LST and/or body cell mass (BCM) that DXA actually measures. DXA scans are also used to assess adiposity in children, especially to conduct clinical research.
The U.S. Preventive Services Task Force recommends that women over the age of 65 should get a DXA scan. The date at which men should be tested is uncertain but some sources recommend age 70. At risk women should consider getting a scan when their risk is equal to that of a normal 65-year-old woman.
A person's risk can be measured using the World Health Organization's FRAX calculator, which 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 phenobarbital or phenytoin, celiac disease, inflammatory bowel disease, and other risks.
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