Bone Mineral Density Test

By: Red Hot Mamas

Published: October 11, 2006

The only way to determine if you are at a risk for osteoporosis is to have your bone mass measured. A special test called a bone mineral density (BMD) test can measure bone density and bone health in various sites of the body.

When repeated, it can be used to monitor rates of bone loss and your response to treatment over time. The test is painless and many don’t even require you to change into an examination robe.

With the information from your BMD test, your doctor or healthcare professional can identify whether you are at risk for fracture. In general, the lower the density of a bone means a higher risk for fractures. Test results will help you and your doctor decide the best course of action for your bone health

Bone mineral density (BMD) tests are painless. Most require very low levels of radiation and are similar to having standard X-rays taken. There are several different types of bone density tests that focus on different parts of the body that are most susceptible to fracture due to osteoporosis.

Who should be tested and how frequently?

If you are concerned about your bone health, your doctor can help you determine if you should have your bones tested. We recommend all women ages 65 and older (regardless of risk factors) be tested.

• Estrogen-deficient women at clinical risk for osteoporosis
• Anyone with vertebral abnormalities
• People receiving or planning to receive long-term steroid therapy (glucocorticoid)
• Individuals with primary hyperparathyroidism
• Individuals being monitored to assess the response or efficacy of an approved osteoporosis drug therapy.

Types of BMD Tests

You can expect different types of machines for each kind of screening.  Portable machines can measure bone density in the wrist or heel.  Other machines use low-dose x-ray machines where a scanner passes over your body as you lay on a cushioned table.  These machines usually measure bone density in your hip and lower spine.Your doctor can determine the best method for you. Types include:

DEXA or DXA (Dual Energy X-ray Absorptiometry)

This is considered the most accurate test for bone density because it can detect bone loss after about a 1% change.  The test lasts 10 minutes and measures the spine, hip, or total body.

SXA (Single Energy X-ray Absorptiometry)

Measures the wrist or heel

pDXA (Peripheral Dual Energy X-ray Absorptiometry)

This test is a modification of the DEXA technique that measures bone density of your limbs like the wrist, heel, or finger.

RA (Radiographic Absorptiometry)

Uses an X-ray of the hand and a small metal wedge to calculate bone density.

DPA (Dual Photon Absorptiometry)

This test usually has a slower scan time than the other methods but it can measure bone density in the spine, hip, or total body.

SPA (Single Photon Absorptiometry)

Measures bone density in the wrist

QCT (Quantitative Computed Tomography)

A higher radiation method of measuring bone density from bones in your limbs, such as the wrist.

Ultrasound

Generally used as an initial screening, it uses sound waves to measure density at the heel, shin bone, and kneecap.

Bone Mineral Density Test Results

Your bone mineral density reading will be compared to standards determined by average readings for 1) people your age and 2) those of a healthy, 30 year old (with optimal or peak density). When comparing your BMD to other people of your age, sex and race it is called a Z-score.  If you receive a negative value on your report, it means you have thinner bones (lower bone density) than the average people in your group.  A positive value means you have stronger bones (a higher bone density) than others in your group.

When comparing your BMD to the average score of a healthy 30 year old, it is called a T-score.  It is statistically derived; if you receive a negative value on your report, it means you have weaker bones than an average 30 year old.  A positive value indicates you have stronger bones than an average 30 year old.

It is important to keep in mind that low BMD values may be derived from other disorders aside from osteoporosis.  For example, hyperthyroidism, hyperparathyroidism, multiple myeloma, Cushing’s Syndrome, ankylosing spondylitis, rickets, premature menopause or a vitamin D deficiency.  Discuss your results thoroughly with your healthcare practitioner to consider the whole picture of your BMD readings. {rt}