Get answers to your Osteoporosis, Metabolic Bone & Mineral Disorders questions.
BMD test; Bone density test; Bone densitometry; DEXA scan; DXA; Dual-energy x-ray absorptiometry; p-DEXA
A bone mineral density (BMD) test measures how much calcium and other types of minerals are present in a section of your bone. Your health care provider uses this test, along with other risk factors, to predict your risk of bone fractures in the future and detect osteoporosis. Bone fracture risk is highest in people with osteoporosis.
Several different kinds of machines can do BMD testing. The most common and most accurate method is called a dual-energy x-ray absorptiometry (DEXA) scan. It uses low-dose x-rays (about 1/10th the radiation dose of a chest x-ray).
There are two different types of DEXA scans:
A central DEXA scan that measures bone density in your lower spine or hip is the best test to predict your risk of fractures.
Remove any jewelry before the BMD test. Inform your health care provider if you may be pregnant.
The scan is painless, although you will need to remain still during the test.
Bone mineral density (BMD) tests are used to detect osteoporosis, the thinning of bone tissue and loss of bone density over time.
BMD testing or screening should also be done in the following people, who are thought to be at an increased risk for osteoporosis:
If you are being treated for osteoporosis, BMD testing can help your health care provider monitor your response to treatment.
The results of your test are usually reported as a "T score" and "Z score."
In either score, a negative number means you have thinner bones than the standard. The more negative the number, the higher your risk of a bone fracture.
A T score is within the normal range if it is -1.0 or above.
Bone mineral density testing does not diagnose fractures. However, along with other risk factors you may have, it helps predict your risk of having a bone fracture in the future. Your doctor will help you understand the results.
Treatment recommendations depend on your total fracture risk.
BMD testing involves exposure to a low level of radiation. Most experts feel that the risk is very low compared with the benefits of identifying osteoporosis before you break a bone.
Simple bone density scans using portable machines may be available as part of health fairs or screenings. These portable scanners may check the density of your wrist or heel. However, keep in mind that hip and spine scans are more reliable.
Lim LS, Hoeksema LJ, Sherin K; ACPM Prevention Practice Committee. Screening for osteoporosis in the adult U.S. population: ACPM position statement on preventive practice. Am J Prev Med. 2009;36:366-375.
National Osteoporosis Foundation. Clinician's Guide to Prevention and Treatment of Osteoporosis. Washington, D.C.: National Osteoporosis Foundation; 2008.
Nelson HD, Haney EM, Dana T, Bougatsos C, Chou R. Screening for osteoporosis: an update for the U.S. Preventive Services Task Force. Ann Intern Med. 2010;153:99-111.
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