Bone density testing

Bone density testing is a medical procedure used to measure the density, or strength, of your bones. It can identify osteoporosis (when bones become less dense, lose strength and break more easily because of calcium loss) or osteopaenia, a milder form of bone loss. The test, also known as bone mass measurement, can also help estimate the risk of future fractures.

Several different procedures can measure bone density, and most are quick and pain-free. Dual energy x-ray absorptiometry (DEXA) is the most widely used technique because it is fast and highly accurate.

When bone density testing is performed#

Bone density testing is most often used for people who have:

• had a previous fracture
• osteoporosis, or who are postmenopausal and concerned about osteoporosis
• a vertebral (spinal) deformity
• osteopaenia (decreased bone density)

Osteoporosis is common in older people, particularly women. Certain diseases and conditions can also contribute to bone loss, including endocrine (hormonal) disease, chronic liver disease, rheumatoid arthritis and chronic kidney (renal) failure.

Medical issues to consider#

Before the test, discuss a range of issues with your doctor, including:

• your medical history
• your risk factors for bone disease
• whether you are or might be pregnant, since pregnant women should not undergo bone density testing
• any special instructions to follow before the test

In most cases you will be asked to undress and put on a hospital gown, and all jewelry must be removed before the test.

Test procedures#

Several procedures can be used to measure bone density:

• Dual energy x-ray absorptiometry (DEXA) – x-ray beams of differing energy are used to measure bone and soft tissue density separately. It can measure bone density in the spine, hip, forearm and the whole body, and is one of the most common methods because it is fast and highly accurate.
• Single energy x-ray absorptiometry – a single x-ray beam measures bone density at peripheral sites such as the forearm and heel. The area being tested is wrapped in a tissue-like substance or immersed in water to improve the quality of the results.
• Ultrasound – measurements taken during an ultrasound can provide information about the structural integrity of bone. Newer devices, such as quantitative ultrasound (QUS), can estimate the bone density of the heel within minutes and produce an automatic printout of results.

Immediately after the procedure#

Most bone density scans take around half an hour, and you can go home straight away. You will need a follow-up appointment with your doctor to discuss the results.

What the measurements mean#

Bone density measurements are reported as a value in g/cm2, and as a T-score or Z-score. These scores describe your measurement in relation to a reference population:

• the T-score compares you with young adults of the same sex
• the Z-score compares you with people of the same age and sex

Osteoporosis is diagnosed if your T-score is -2.5 or less.

Possible complications#

Bone density testing is a safe, painless procedure with no after-effects. The dose of radiation is roughly the same as you would receive from the general environment in about one day. You can resume your normal activities as soon as the test is finished.

Taking care of yourself and long-term outlook#

If you have osteoporosis, you may need repeat bone density tests to check that your treatment is helping to preserve your bones. Try to have all future tests at the same facility using the same machine, which rules out measurement differences between machines or facilities.

Other types of tests#

Standard x-rays can only detect osteoporosis once around one-third of the bone mass has already been lost, so they cannot detect it in the early stages. However, your doctor may still request regular x-rays to make sure your symptoms are not caused by another condition, or to check for bone fractures.

Key points#

• Bone density testing measures the strength of your bones and can identify osteoporosis or osteopaenia and estimate fracture risk.
• DEXA is the most common method because it is fast, accurate and painless, with a very low radiation dose.
• Results are reported as a T-score and Z-score; osteoporosis is diagnosed when the T-score is -2.5 or less.
• Standard x-rays only detect osteoporosis after about a third of bone mass is lost, so they cannot find it early.

Where to get help#