Osteoporosis is diagnosed in two ways:

1. An unexplained fracture
   If other causes of bone abnormalities have been ruled out, individuals 40 years of age and over who have a fracture after a minimal injury (such as a fall from standing height), by definition, have osteoporosis. One of the goals of the Osteoporosis Program at Women’s College Hospital is to identify women and men at high risk for fracture before a fracture occurs.

1. By measuring bone density
   Bone density tests measure a person’s bone mass. The test measures the density of a woman’s bone and compares it to the bone mineral density (BMD) of healthy, young women. The denser the bone, the less likely it will fracture. Conversely, the lower the bone density measure, the greater the risk of a non-traumatic fracture. Some studies have shown that measuring the bone density of women 65 years of age and older can help predict a woman’s risk of fracturing a bone.

Bone mineral density is typically assessed using DXA (dual energy x-ray absorptiometry).

DXA

DXA (dual energy x-ray absorptiometry) is the current gold standard for measuring bone density. DXA measures bone density of the lower spine, the hip and, in some cases, the wrist.

This specialized x-ray technique measures bone mass, and then uses a computer program to compare a person’s bone density to that of a young, healthy individual of the same sex. This comparison generates a T score. The T score represents the number of standard deviations you are above (positive T score) or below (negative T score) the healthy young adult.

Advantages
DXA testing has several advantages. It is:

• painless
• non-invasive
• usually accurate and precise
• uses a low level of radiation (less than ¹⁄₃ of a chest x-ray)

DXA is less helpful when a person has arthritis in the hips or spine, or when a person has had hip or back surgery.

Limitations
In 1994, the World Health Organization developed guidelines for diagnosing osteoporosis based on DXA results. These guidelines are used by many facilities that perform DXA testing in Canada. According to these guidelines, bone density can be qualified as:

• normal (T score > -1.0)
• osteopenic (T score < -2.5)
• osteoporotic (T score < -2.5)

While these classifications are helpful, they only tell us about the quantity of the bone, not the quality of bone. Poor bone quality is the reason why many women with normal T scores have fractures; and good bone quality explains why there are people with very low T scores in the osteoporotic range, who do not have fractures.

Several tools have been developed to take into account bone quality and bone quantity when evaluating a patient’s fracture risk.

What to expect
When you go for your DXA test, you will be asked to lie down on a table while your spine, a hip, or both your spine and hip, are scanned. The test lasts about 20 minutes. It is non-invasive and causes no pain or discomfort.

At Women's College Hospital
DXA testing is available at Women's College Hospital, as part of the Osteoporosis Program’s one-stop patient-centred approach.

DXA testing is covered by the Ontario Health Insurance Plan (OHIP). A doctor's referral is needed for this test.