DXA Scan. How Often

The New England Journal of Medicine

The New England Journal of Medicine (Photo credit: Wikipedia)

What is a DXA scan? How often should I have a DXA scan?

A DXA scan is test of X-ray absorbiometry by sending two X-rays into a bone from different directions, each of which is of a different energy level. The level of absorption dictates the level of density or porosity the bone may have.  Though there are other methods of testing bone mass density, the DXA scan is the most accurate and repeatable, as well as widely available test.

The study tracked 4957 women ages 67 and over more than 10 years. The women had a DXA scan when they began the study and were not osteoporotic.  This study indicates that for women who show no indication of osteoporosis at the age of 65, the next time to perform a DXA scan may be as far out as 15 years provided nothing takes place that could compromise bone mass. Currently, Medicare is allowing for a retest rate of two years. Steven Cummings, a researcher from the University of California, San Francisco was quoted in the New York Times as saying, “bone density testing has been oversold.”

This is part of a broad rethinking of how to diagnose and treat this bone disease that can manifest in broken hips and collapsing vertebrae. The data analysis indicates that less than 1 percent of women with normal bone density, and fewer than 5 percent with mildly low bone density, developed osteoporosis in the ensuing 15 years after the initial DXA scan. But of those with low bone density at the beginning of the research project, who were near the classification of osteoporosis, meaning 2.5 standard deviations from the reference level, 10 percent became osteoporotic in approximately one year.

Bone density screening tests such as DXA scans, have increased in volume since the release of the bisphosphonate drugs, such as Fosamax. These drugs were originally prescribed to prevent osteoporosis, but now are only prescribed to osteoporotic patients with a higher risk of fracture. Upon release, these drugs were widely prescribed and used as preventative measures, as well as prescribed indefinitely. The long-term side effects have called this practice to question. Physicians now favor the prescription of bisphosphonate pharmaceuticals for deconditioned, elderly patients, but not for younger patients. For individuals who are not deconditioned or elderly, practical methods for inducing axial mechanical loading on the skeletal structure should be used. Currently, devices are being deployed in medical/wellness facilities to satisfy this need.

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