Exams and Tests for Osteoporosis

By knowing, monitoring, and protecting your bone health, you can potentially avoid an osteoporosis diagnosis. If you think you might be at risk for this bone disease (see Causes of Osteoporosis for a list of risk factors), you should be proactive. Otherwise, most people find out they have osteoporosis when they break a bone.

Who Needs to be Tested for Osteoporosis?

• Someone who has an x-ray that reveals low bone mass, which could mean osteopenia or possibly osteoporosis
• Women who begin menopause before age 45 and who are not taking estrogen (e.g., Estrogen Replacement Therapy, ERT)
• A woman age 65 or older
• A post-menopausal woman who has one or more of the osteoporosis risk factors—and especially if she's had a fracture
• A man age 70 or older
• A man age 70 or younger who has one or more of the osteoporosis risk factors
• A family history of osteoporosis
• Steroids have been (or are) taken regularly
  
• Presence of hyperthyroidism, diabetes, liver/kidney disease, rheumatoid arthritis

Bone Mineral Density (BMD) Test
One of the best and most common ways to monitor your bone health is by having a bone mineral density (BMD) test. That will let you know how strong your bones are in particular areas—how dense they are. If you don't already have osteoporosis but could be at risk, a BMD can help your doctor predict your likelihood of having a fracture. Repeated BMD tests allow the doctor to compare the results and see if you're losing bone or maintaining it.

A BMD is also used to confirm an osteoporosis diagnosis; in fact, it's the only test than can diagnose osteoporosis.

Whether you're having a BMD test done to confirm osteoporosis or you just want to monitor your bone health, the actual test is done in the same way. To find out your BMD, your doctor will use a special type of x-ray called dual-energy x-ray absorptiometry (DXA). He or she will most likely scan your hip or your spine because those are the areas most prone to fracture.

The whole test doesn't take long—maybe 5-10 minutes. Don't worry about radiation exposure—it really isn't much. You should get the results on the same day.

T-score and What it Means
The doctor will then analyze your bone density and give it a T-score. A T-score is a number derived by comparing your BMD tests results to an average score for a healthy adult of your sex and race who has reached their peak bone mass (usually around age 25).

The T-score signifies how far you are from "normal." It's the difference between your BMD and the BMD of someone at peak bone mass. T-scores can be as low as one standard deviation (SD, a statistical term) below normal and still be considered healthy. Patients with T-scores between -1 SD and -2.5 SD have osteopenia and are considered at high risk for developing osteoporosis. Patients with T-scores lower than -2.5 SD have osteoporosis.

Here's a table that summarize that information:

Your doctor will decide how often to repeat the BMD test. If you've already been diagnosed with osteoporosis, you may have to have it every year or two so that your doctor can see if your treatments are working properly. He or she will be able to tell that by comparing the T-scores.

Z-score and What it Means
Not everyone gets a T-score. Women who haven't yet gone through menopause and men younger than 70 will still have the BMD test done with DXA, but they will get a Z-score. Instead of comparing your BMD to a 20-something, your doctor will compare it to the normal BMD for someone your age, sex, body type, and race.

Z-scores work just like T-scores: they tell the standard deviation from normal. If you have a low Z-score, your doctor may recommend further testing to see why you have low bone density.