Published on March 31, 2014
The most common bone density test used today is called a dual energy x-ray absorptiometry (DXA). This test involves lying on a table for several minutes while a small x-ray detector scans your spine, one hip, or both. You may be asked to lift your legs onto a support to straighten your back for the test. The test is safe and painless and does not require any injections or cause any discomfort. You will receive a very small amount of radiation from a DXA test, which is approximately the same amount you are exposed to if you fly from Toronto to Vancouver.
How Does a Bone Densitometer Measure Bone Density?
Think of the light shining through the curtains of your home on a sunny day. The amount of light that reaches your eye depends on the thickness of the curtains. If your curtains are very thick, very little sunlight passes through them. If, however, you replace them with a thinner fabric, the light coming through will increase substantially. Similarly, a bone densitometer uses a detector to measure the transmission of small amounts of x-rays (light) through your bones. The amount of light that passes through the bone is measured, thus providing a radiologist with a picture, which indicates how dense (thick or thin) your bones are.
Who should get a Bone Density Test?
- All women and men 65 years or older
- Postmenopausal women and men 50 – 64 with risk factors for fracture including:
- Fragility fracture after age 40
- Vertebral fracture or low bone mass identified on x-ray
- Parental hip fracture
- High alcohol intake
- Current smoking
- Low body weight, i.e. less than 132 lbs or 60 kg
- Weight loss since age 25 greater than 10%
- High risk medication use: prolonged glucocorticoid use, aromatase inhibitors for breast cancer, androgen deprivation therapy for prostate cancer
- Rheumatoid arthritis
- Other disorders that may contribute to bone loss
- Younger men or women (under 50) with a disease or condition associated with low bone mass or bone loss:
- Fragility fractures
- High-risk medication use (steroid use, aromatase inhibitors, androgen deprivation therapy)
- Rheumatoid arthritis
- Other chronic inflammatory conditions
- Cushing’s disease
- Malabsorption syndrome
- Uncontrolled hyperthyroidism
- Primary hyperparathyroidism
- Hypogonadism; Early menopause (< 45)
- Other disorders associated with rapid bone loss/fractures