New report: thumbs down on bone scans for osteoporosis

As they approach menopause, more and more women are being advised to undergo bone mineral density (BMD) measurement, not because they've shown any symptom of bone-thinning, but merely because they have reached that stage of life. Many gynecologists advise testing because they believe that low bone density predicts a future hip fracture and thus a need for estrogen therapy. This widespread medical advice, unfortunately, runs counter to the findings of a new report from the British Columbia Office of Health Technology Assessment. The report concluded that the research evidence does not support BMD testing of well women at or near menopause as a means to predict future fractures. One can have low bone mass at age 48, for example, and not suffer a hip fracture in old age. Conversely, one can have good bone density at age 48 and have a hip fracture at age 79.

"The greatest concern is that BMD measurement will mislabel most women. More than half of the women who will eventually suffer fractures will be classified as normal," according to Dr. Arminee Kazanjian, report co-author, "The majority of women who will ultimately suffer fractures will not get appropriate treatment because the focus is on the minority with low bone density, most of whom will not suffer fractures." Despite the medical emphasis on bone loss, it is merely one of many factors implicated in hip fracture. The majority of falls among the elderly do not result in fracture, but the 5% that do are associated with risk factors like impaired vision, poor muscle strength, and long-acting tranquilizers. In fact, the report found that the presence of several such risk factors was a stronger predictor of hip fracture than low bone density.

The new report from British Columbia is actually a review of all reviews. Over the last few years as BMD measurement became more widespread, various professional organizations around the world have reviewed the topic of BMD and published testing recommendations. The British Columbia report excluded all the reviewing organizations, such as the American College of Obstetricians and Gynecology, which made recommendations without conducting a systematic assessment of all relevant studies. That left 14 evidence-based reviews from such organizations as the Swedish Council on Technology Assessment. The British Columbia report based its negative conclusion on an analysis of all 14 evidence-based reviews.

Enthusiasm for measuring BMD is driven by the availability of new drugs to preserve bone density, most recently, the so-called designer estrogen called Evista. After identifying a massive increase in BMD testing between 1989 and 1996 in North America, the British Columbia report noted, "It is not coincidental that during this time period the pharmaceutical and device industries strongly supported extensive advertising to raise awareness about osteoporosis and urge both doctors and consumers to intervene." But there's doubt about the efficacy of the two most widely used preventive measures. Here's how the U.S. Preventive Services Task Force 1996 Report put it: "Due to the long delay between menopause and fracture, few prospective studies have been able to demonstrate directly that these interventions [calcium supplements and estrogen] reduce fracture."

For the most widely used bone density test called Dual-Energy X-Ray Absorptiometry (DXA or DEXA), the person lies fully clothed on a table for about one minute while the arm of an x-ray machine passes over her hips and spine. Last month, the U.S. Food and Drug Administration approved a new device for assessing the condition of a person's bones by measuring the density of the heel with ultrasound. The new test has several advantages over DXA. There is no radiation exposure, less expense, and more convenience (the patient slides a foot into a small machine and get results minutes later). Both tests, however, share the same major problem--they cannot accurately predict hip fracture.

Resources:

"Bone Mineral Density Testing: Does the Evidence Support Its Selective Use in Well Women?" Request your free copy by fax (604-822-7975) or e-mail (bcohta@chspr.ubc.ca). For information about exercises to prevent hip fracture, see HealthFacts, June 1997: "New Book: Strong Women Stay Young."

COPYRIGHT 1998 Center for Medical Consumers, Inc.
COPYRIGHT 2000 Gale Group