To understand a bone density test, you must know how the test is performed, how the results are interpreted and who is recommended as a candidate for the procedure. If your doctor has recommended that you have the test, you will require only minimal preparation. Although bone density testing does necessitate exposure to a low level of radiation, the risk is low compared to the dangers of untreated bone loss.
Purpose
Most commonly, doctors use bone density tests to diagnose osteoporosis, a condition involving a slow loss of calcium which causes the bones to become fragile, thin and susceptible to breaking. Although osteoporosis most often affects post-menopausal women, it can also be a problem for men. A physician can also use bone density tests to track the effectiveness of therapy for osteoporosis, or to determine a person's risk for developing a bone fracture. Besides age, factors such as body weight, family history, previous fractures, smoking and alcohol consumption can all affect a person's likelihood of breaking a bone.
Who Should Have the Test
Your doctor may recommend that you have a bone density test if you are are past the age of menopause and not taking estrogen. If you use medications including corticosteroids, high-dose thyroid replacement drugs some anti-seizure medicines, you may also have increased bone loss, according to the website RadiologyInfo.org. Certain health problems, including type 1 diabetes, kidney disease, liver disease, hyperparathyroidism and some thyroid conditions can also increase your risk of fracture.
Preparation and Testing
A bone density test is quick--taking only about 10 minutes--and is painless and non-invasive. Your doctor will instruct you to discontinue use of calcium supplements for at least 24 hours prior to the test. She will also want to know if you have had any recent oral contrast or nuclear medicine tests, as these could affect the results. Plan to wear loose clothing with no metal fasteners or zippers. During the test, you will lie on a padded platform while an instrument passes over your body, measuring your bone density at the hip or the spine through a dual energy X-ray absorptiometry scan, or DXA scan. Although some drug stores offer testing using small portable machines which measure bone density of your finger, wrist or heel, such exams are not as accurate and precise as a DXA scan of the spine or hip, according to the Mayo Clinic website.
Interpreting Test Results
Results of a bone density test are usually given as a "T score" and a "Z score," according to the MedlinePlus website. While the T score shows your bone density in relation to a healthy young person, the Z score compares your bone density to others of your age, gender and race. With either score, negative numbers indicate thinner bones than usual. A T score of -1.0 or above is considered in the normal range. A T score which is between -1.0 and -2.5 is an indication of osteopenia, meaning that you are at risk of developing osteoporosis. If your score falls below -2.5, you are considered to have osteoporosis.
