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What is a bone density test?

A bone density test uses dual energy x-ray absorptiometry (also called DXA) to see how many grams of minerals are inside a piece of bone. It usually measures the vertebrae or hip because those bones are most likely to be affected by osteoporosis. During the test you usually lay down while a machine passes over your body for about five to fifteen minutes. It is fairly quick and non-invasive. Sometimes a smaller device called a pDXA (peripheral DXA) may be used to check a wrist, finger, or heel, or an ultrasound device may be used to test the heel, but the DXA is considered the best test available.

Medical Professionals use the measurement of Bone Mineral Density (BMD) to help determine whether a patient has osteoporosis. A bone mineral density (Dual X-ray Absorptiometry, DXA) scan is an exam that measures your actual bone mass, very much like an x-ray that measures how dense the bones are at the hip and the lower spine. Sometimes, the density is also measured at the arm. A DXA is completely painless and takes just a few minutes. We usually manage to arrange a scan for the same day when we see patients who are suspected to have osteoporosis. Your score along with other risk factors will help determine if you are at risk for fracture.
A bone density test is used to:
  • measure the effectiveness of medical treatment of osteoporosis. Your doctor might want you to undergo a bone density test to check how well antiresorptive drugs are treating your osteoporosis. These drugs often increase bone density 5% or more during the first year of treatment. However, any difference in two successive tests that is less than 5% is more likely to be due to random error than to an actual change in the status of your bones. It takes at least a year to find out if (and by how much) the medication has increased bone density.
  • determine whether you're experiencing faster-than-average bone loss. Sometimes a doctor will recommend bone density tests to see if your bone loss is faster than average. One test is performed to gather information that serves as a starting point, and then another test is performed about 5 years later. A woman with an average rate of bone loss might have a drop of 5% in bone density after a 10-year period. In contrast, a woman with abnormally rapid bone loss could have a difference large enough to be detected by this second test 5 years later.
  • routinely test all postmenopausal women for osteoporosis. Some doctors believe that all postmenopausal women should undergo bone density tests. In general, a test is considered an appropriate screening tool if its benefits outweigh its risks. In the case of bone density tests, the benefit is the reduction of fractures following the identification and treatment of definite osteoporosis. The risks would be the cost of testing all women, the possible adverse side effects of treatment, and the cost and consequences of misdiagnosis.

Expert panels of specialists in osteoporosis in the United States and other countries have looked carefully at the evidence. The U.S. Preventive Services Task Force recommends that women age 65 and older be screened routinely for osteoporosis. For women at increased risk of osteoporosis, routine screening should begin as early as age 60. Bone density testing is most useful as part of the diagnostic efforts for women known to be at risk of osteoporotic fractures."

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.