Bone density scans are used to measure bone mineral content and density. A bone density test is painless and non-invasive, and mainly used to look for osteoporosis (thin, weak bones) and osteopenia (decreased bone mass). The test is used to measure the density of the spine, lower arm and hip.
The dual-energy X-ray absorptiometry (DXA) version of bone density scanning is considered the most accurate test. During a DXA scan, you lie down for five to 10 minutes while a machine scans your body. With this test you are exposed to a small amount of radiation—less than the amount in a normal chest X-ray.
After the test, a T-score is given for each site measured. A negative score means you have thinner bones than an average 30-year-old woman. A positive score means you have stronger bones than an average 30-year-old woman. If the T-score at any site is -1 to -2.5, you have a low BMD and are at increased risk of osteoporosis. A score of -2.5 or lower means that you have osteoporosis. Treatment usually is recommended to prevent fractures.
All women aged 65 years or older should have a bone density test. Women who are younger than 65 years and past menopause should have a bone density test if they have had a bone fracture because of fragile bones or have other risk factors for osteoporosis, such as rheumatoid arthritis, smoking, alcoholism, a history of hip fracture in a parent, or a body weight less than 127 pounds.
Women 65 years and older with normal bone mass or mild bone loss should have a test every 15 years. More frequent testing is recommended for women in this age group with T-scores between -1.5 and -2.49.
Source: American College of Obstetricians and Gynecologists.