A Bone Mineral Density (BMD) test is a non-invasive and pain-free test that measures the density of your bones to determine your likelihood of developing osteoporosis or enduring an osteoporosis-related fracture. The bones that are most commonly tested are in the spine, hip and sometimes the forearm.
A bone density test uses X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone. The higher your bone mineral content, the denser your bones are. And the denser your bones, the stronger they generally are and the less likely they are to fracture.
Although osteoporosis is more common in older women, men also can develop the condition. Regardless of your sex or age, your doctor may recommend a bone density test if you have:
- Lost height: People who have lost at least 1.6 inches (4 centimeters) in height may have compression fractures in their spines, for which osteoporosis is one of the main causes.
- Fractured a bone: Fragility fractures occur when a bone becomes so fragile that it breaks much more easily than expected. Fragility fractures can sometimes be caused by a strong cough or sneeze.
- Taken certain drugs: Long-term use of steroid medications, such as prednisone, interferes with the bone-rebuilding process, which can lead to osteoporosis.
- Received a transplant: People who have received an organ or bone marrow transplant are at higher risk of osteoporosis, partly because anti-rejection drugs also interfere with the bone-rebuilding process.
- Lower than normal hormone levels: In addition to the natural drop in hormones that occurs after menopause, women’s estrogen may also drop during certain cancer treatments. Some treatments for prostate cancer reduce testosterone levels in men. Lowered sex hormone levels weaken bones.
BEFORE THE TEST
Bone density scans require minimal preparation:
- Avoid wearing jewelry or any metallic objects on your body, as well as clothes with metal clips, snaps, buttons or zippers on the day of your test.
- Do not take calcium/vitamin supplements for 24 hours prior to examination.
- If you have had a nuclear medicine dye injection or a barium study within the past two weeks, please reschedule your BMD test.
- Please ensure you bring your health card and doctor requisition.
DURING THE TEST
You may be required to wear a gown during your bone density scan. An X-ray machine will scan the areas that are common to bone degradation including your back and hips. There is minimal physical contact with the machine during the test.
AFTER THE TEST
Once the test is completed, you will be able to return to your normal activities.
WHAT TO BRING
To avoid delays on the day of your test, ensure that you bring your health card and your requisition.
BMD Measurement Information
|< 50 years||Below expected range for age||Z-score ≤ -2.0|
|Within expected range for age||Z-score > -2.0|
|> 50 years||Severe (established osteoporosis)||T-score ≤ -2.5 with fragility fracture|
|Osteoporosis||T-score ≤ -2.5|
|Low bone mass||T-score -1.0 to -2.5|
|Normal||T-score ≥ -1.0|
Z-score: number of standard deviations above (+) or below (-) the mean density for an individual of that age and sex.
cFracture Risk: (10-year absolute): low (<10%) moderate (10% to 20%), or high (>20%). Fracture risk predicted for an individual by this system applies only for a finite period of time, and that risk will change with advancing age or with the development of new clinical risk factors. Based on 2010 CAROC system. Papaioannou, A et al. 2010 clinical practice guidelines for the diagnosis and management of osteoporosis in Canada: summary. CMAJ 2010;182:1864-73.
dFor the purpose of second and subsequent testing (MOHLTC Schedule of Benefits, 2010)
“high risk patient” means a patient:
1. at risk for accelerated bone loss (in the absence of other risk factors, patient age is deemed not to place a patient at high risk for accelerated bone loss); or
2. with osteopenia or osteoporosis on any previous BMD testing, or
3. with bone loss in excess of 1% per year as demonstrated by previous BMD testing.
High risk patient is limited to a maximum of one test every 12 months unless the ordering physician obtains written prior authorization from a medical consultant.
“low risk patient” means a patient who is not a high risk patient. Limited to a maximum of one second test not earlier than 36 months following baseline; subsequent test not earlier than 60 months following the second or any subsequent test.