Osteoporosis

Overview

An initial examination for osteoporosis is recommended at menopause if you have risk factors. This assessment will alert you to any problems and allow doctors to prescribe treatments to curb bone loss and monitor your condition as you grow older. To determine if you have osteoporosis or may be at risk for the disease, your doctor will ask you a variety of questions about your lifestyle and medical history. Your doctor will want to know if anyone in your family has suffered from osteoporosis or if they have had bone fractures.

Based on a comprehensive medical assessment, your doctor may recommend that you have your bone mass measured. A specialized test called a bone mineral density test (BMD test), which is also appropriate for men when they reach age 70 and have additional risk factors, can measure bone density in various sites of the body. A bone density test can detect osteoporosis before a fracture occurs, predict your chances of having a fracture in the future, determine your rate of bone loss, and/or monitor the effects of treatment if the test is conducted at intervals of a year or more.

BMD tests are X-rays that use very small amounts of radiation to determine the bone density of the spine, hip, wrist, or heel. The most commonly used test, considered the standard, is known as a DEXA (dual energy X-ray absorpitometry) test.

In this section on testing, you will find information on:

• Who should be tested
• The DEXA test
• Understanding the results of a bone mineral density test

BMD

Does bone mineral density (BMD) testing make sense for you?

The National Osteoporosis Foundation Physician's Guide to Prevention and Treatment of Osteoporosis suggests BMD testing for the following post-menopausal women:

• Those from menopause to age 65 with one or more additional risk factors for osteoporotic fracture (besides menopause)
• Those who have had a fracture (broken bone)--to determine if osteoporosis is the underlying cause
• All those who are age 65 or older, regardless of other risk factors
• Those who are considering therapy for osteoporosis, if BMD testing will facilitate the decision
• Those who have been on hormone therapy for prolonged periods

Men age 70 or older should also be tested if they have additional risk factors. For more information, see our sections on risk factors you can modify and risk factors you can't.

Dual energy X-ray absorpitometry (DEXA)

The most accurate method for detecting osteoporosis and other bone diseases is dual energy X-ray absorpitometry (DEXA). This test, which takes about 10 to 15 minutes, measures the bone loss in your hips and spine. It also helps your doctor determine how quickly you are losing bone mass if compared to a prior measurement, as well as predict your risk of fracture. The test is also used to follow the course of the disease and monitor the effects of various treatments. Different BMD tests may measure your hip, spine, wrist, finger, shinbone, or heel.

Retail stores sometimes sell a smaller version of the DEXA machine that measures bone mass in your forearm. However, these readings do not reflect the bone loss in your hips and spine, where the most common debilitating fractures occur. Medicare now covers bone density testing for many patients, as required in the Bone Mass Measurement Act of 1998.

How to prepare: You do not have to change your daily routine before this test. Eat, drink, and take your medications as you normally would. However, do not take calcium supplements (such as Tums) for 24 hours before your bone densitometry test. If you think you may be pregnant, notify your physician.

What to expect: You must wear a hospital gown while the technologist performs the test. No needles or injections are involved. The DEXA procedure is similar to having a standard X-ray. The amount of radiation used is very small.

After the test: Generally, you can resume your usual activities immediately. The results of your test will be reviewed by a specially trained technologist and board-certified physicians. Your test results will be provided to your physician, who will discuss the results with you.

Interpreting the BMD

Your bone mineral density (BMD) test result is compared with two norms, "young normal" and "age-matched." Young normal, known as your T-score, compares your BMD test result to the optimal or peak density of a 30-year-old healthy adult. Age-matched, known as your Z-score, compares your BMD test result with what is expected for someone your age and with a similar body size. Among older adults, however, low BMD is common, so comparison with age-matched norms can be misleading.

Scores below the norm are indicated in negative numbers. For example, a score from -1 to -2.5 indicates low bone mass, or osteopenia, and a score of below -2.5 is considered a diagnosis of osteoporosis. For most BMD tests, a drop of one unit equals a 10 to 12 percent decrease in bone density. If the Z-score is especially low, your physician may need to order further tests to make sure that other processes are not causing the low density, rather than primary osteoporosis.

This BMD measurement is not the only thing that indicates an increased risk of fracture, though it is an important tool. Talking to your physician about other matters, such as your risk of falls, is also important.