UCSF Study Finds Bone Density Test Results Can Be Misleading

March 07, 2000
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Many women who are being treated for osteoporosis with medications are checked periodically with measurements of bone density. About one out of five women taking these medications appear to lose bone density during the first year of treatment, causing doctors to change the treatment. But this loss may be misleading, according to a UC San Francisco study.

The study results, published in the March 8 issue of the Journal of the American Medical Association, showed that women with the greatest amount of bone density loss during the first year of treatment were the most likely to gain bone density when the same treatment was continued, said lead author Dr. Steven Cummings, an internist and epidemiologist at UCSF Medical Center.

When an osteoporosis patient loses bone density during the first year of treatment with alendronate or raloxifene, physicians often change the treatment because they believe the medicine is not working for the patient, Cummings said. But this may not be the best course of action for physicians to take, he said.

"It's important if women are being monitored by periodic tests of bone density and they lose bone in the first year or two to not change treatment," Cummings said. "Most doctors would have changed or stopped the treatment. They say the woman hasn't responded so they often switch her to another drug or add a second drug. Adding a second drug adds costs, risks and side effects. This study shows that patients should make sure they are taking the drug regularly and properly but should not change the treatment or add another one."

The study examined the results of studies of 2,634 women who were taking 5 milligrams of alendronate daily for treatment of osteoporosis and 3,954 women taking 60 or 120 milligrams of raloxifene daily. Of the women who lost bone density during the first year of treatment with either agent, more than 80 percent gained bone density the second year. Conversely, when the researchers looked at women who gained a large amount of bone density the first year -- a gain of more than 8 percent -- the majority lost an average of 1 percent bone density the second year.

Usually, women taking raloxifene or alendronate for osteoporosis gain 1 percent to 3 percent in bone density during the first year of treatment, Cummings said "When your changes are different than the average -- if you gain more or lose more than is expected -- in the first year you are probably gaining or losing because of errors in the measurement," he said. How a patient is positioned while undergoing the test or how the machine is working on a particular day can cause small errors.

The bone density test works by passing low doses of X-ray beams through a patient's spine, hip or in some cases the forearms and entire body as she lays on a table. The machine measures the amount of X-ray absorbed by calcium in the body. This shows how much calcium is in the bone, an indicator of how much bone density has been lost or gained. The test is an excellent way to determine a woman's risk of getting a fracture, whether she has osteoporosis or what kind of treatment she needs, Cummings said. But it may not be the best method of monitoring treatment results for this disease that affects 10 percent to 15 percent of postmenopausal Caucasian and Asian women. The rate is lower in Hispanic and African-American women because they have higher bone density.

"This study does raise doubts about whether it's really worth while to get periodic measurements of bone density to monitor treatment," Cummings said. "The practical meaning of this is don't be stressed out by losing bone density during treatment. If the tests show that you have lost bone, make sure you are taking the drug regularly and correctly. But don't change treatment. If you gain a lot, don't get too excited because your measurements may slip back the next year."

Data for the study was collected through the Fracture Intervention Trial funded by Merck Research Laboratories and the Multiple Outcomes of Raloxifene Evaluation trial, funded by Eli Lilly and Co. UCSF investigators conducted these analyses without support from either company.