Bone Health Tests
Organizations like the National Institutes of Health call low bone density, or osteoporosis, the “silent disease” because there are no symptoms to watch for. Most cases of osteoporosis are diagnosed after a broken bone or fracture. But there are tests for bone mineral density. The U.S. Preventative Services Task Force recommends that all women get tested at age 65 and continue to get tests in the years after. If you are under 65 but have had breast cancer treatments that can result in bone loss you should ask your doctors if they would recommend getting tested earlier.
The most common test for bone mineral density is the Dual Energy X-ray Absorptiometry scan, usually called the DEXA or DXA scan. In this painless test, a machine scans your body to look at the bones in your wrist, spine and hip while you lay on a table. This will provide information about your bones and is used to diagnose osteoporosis.
The machine never touches you but you must remain very still while the scan is being done. You may be asked to stop taking certain supplements and medicines in the day or two before being scanned and no metal jewelry, metal buttons or zippers can be worn during the scan.
The results from your DEXA scan will include your T-score. This number compares your bone mineral density with that of a healthy 30-year-old and is the most important measure in determining whether you have osteoporosis or low bone density. A T-score of zero would mean your bone density is the same as your doctors would expect for a person whose bones are at their strongest. Your results will place you in one of three categories depending on your score:
- Normal, if your T-score is between +1 and -1
- Osteopenia, or low bone density, if your T-score is between -1 and -2.5
- Osteoporosis, if your score is less than -2.5
Along with your T-score, your doctor will use other information from your scan, your medical history and a physical exam to tell your risk of getting a fracture. With this information you can talk about lifestyle changes you can make to improve your bone health and possible medicines to maintain your bone strength if you are found to have osteoporosis.
Your T-score will be the main factor in telling if you have osteoporosis, but your DEXA scan results will have other scores your doctor may review with you. The bone mineral density score will tell how much tissue your bones contain per centimeter. The Z-score will compare your bone density to what would be expected for a woman the same age as you.
If you have metastatic breast cancer, or your doctors want to make sure you do not have metastatic breast cancer, they may order a different kind of test that is usually called a bone scan. Because the names are similar the two tests are sometimes confused. A bone scan will look for areas of too much cell activity in the bone to determine if the cancer has spread to the bones. A bone density scan, or a DEXA scan, is used to check for osteoporosis and bone loss.