Testing for osteoporosis – how often?

By Dr. Ananya Mandal, MDJan 19 2012

A new study shows that many women who get screened for osteoporosis may not need it. It suggests that the current guidelines result in too many unnecessary tests, increasing costs and sometimes spurring unnecessary treatment.

Osteoporosis, a loss in bone density that can cause fractures and injuries, develops in fewer than 10 percent of women at age 80, if they had normal density at age 65, according to a report today in the New England Journal of Medicine.

The U.S. Preventive Services Task Force, which sets testing guidelines, recommends a bone-density test every two years. Osteoporosis affects about 12 million Americans older than 50, including half of all post-menopausal women at some point, the U.S. task force says. The recommendation for testing every two years was made because not enough is known about how the disease develops, the group has said. The cost of osteoporosis to the U.S. health care system is as much as $18 billion per year.

This new study shows that a healthy result at age 65 probably means woman can wait at least 15 years before being tested again because of how slowly the disease develops. “There’s strong belief that the more we test, the more we are helping patients,” said Margaret Gourlay, a University of North Carolina at Chapel Hill researcher and study author. “This is a good example of why that doesn’t hold up at all.”

Gourlay explained that some doctors prescribe tests every two years because Medicare, the U.S. health plan for those 65 and older, reimburses for the exams on that schedule. The research team tracked patients to gather available evidence to avoid health decisions made on “marketing, advocacy, and public beliefs that have encouraged over testing and over treatment,” the report said. On the other hand lack of information has led some doctors to ignore osteoporosis altogether. Patients don’t remind doctors about osteoporosis screening, which is not as common as mammograms for breast cancer or cholesterol screening, she said.

Each screening costs about $250, Goulay said in a telephone interview. Unnecessary tests can lead to false positives and unnecessary prescriptions of drugs such as Warner Chilcott’s Actonel or Eli Lilly & Co.’s Evista, leading to more patient risk than protection, she said.

The study followed 4,957 mostly white women over 15 years and regularly tested their bone mass starting at age 67. Gourlay said the group’s next goals include gathering data about osteoporosis treatment in men and in women younger than 65.

Gourlay's team found that the best time to have a subsequent bone density test depended on a woman's starting point, as gauged by the so-called T score derived from using X-rays to measure the density of bones in the hip. Lower scores indicated weaker bones. Among women age 67 or older who started out with a normal T score of -1.00 or higher, it took an average of 16.8 years for 10 percent of the group to develop osteoporosis, indicated by a score of -2.50.

They also looked at women with osteopenia, in which “your bones are thinner but not at the osteoporosis level yet,” Gourlay told Reuters Health. As those T scores fell, it took less time for osteoporosis to develop in 10 percent of the women. For women with the lowest starting scores of -2.00 to -2.49, the interval was just 1.1 years. For women with a score of -1.50 to -1.99, it was 4.7 years. And among women who scored -1.01 to -1.49, it took 17.3 years for one in 10 to progress to osteoporosis. The researchers adjusted the analysis to account for estrogen use and risk factors for osteoporosis. The volunteers were women from Maryland, Minnesota, Pennsylvania and Oregon.

“We knew that the groups that had thinner bones to start with were going to transition to osteoporosis faster,” said Gourlay. However, “we were not expecting this kind of separation between the low risk and high risk group. For those women with a T score above -1.5 to have just a 10 percent chance of making the transition to osteoporosis after 17 years was a great surprise. This was very good news.”

However, the time intervals were not the same for all women age 67 and older. They shrank as women aged. “For example, among women with moderate osteopenia, the estimated (bone density) testing interval was approximately 5 years for women who were 70 years old and approximately 3 years for those who were 85 years old.” Gourlay cautioned that the time scales may also be very different for women under 67.

According to Dr. Margery Gass, executive director of the North American Menopause Society, this study “makes a major contribution toward filling a significant knowledge gap in the field of osteoporosis”. Her guidelines for brittle bone disease suggest testing postmenopausal women every two to five years.

“The findings in this paper will enable clinicians to recommend bone mineral density testing from an evidence-based position,” Gass said, adding that testing has been both under-used and over-used, depending on the setting, “primarily because of lack of data to inform guidelines.” It's under-used in women over 65 and over-used “in early postmenopausal women, the majority of whom are at very low risk of fracture,” she said. “Some clinicians are even getting a 'baseline' in early postmenopausal women, something no medical society is recommending.”

Her group recommends screening for all women who are age 65 and older and for women ages 50 to 64 if they are smokers, consume alcohol daily, weigh less than 127 pounds, have rheumatoid arthritis, have already had a fracture suggesting that their bones might be weak or had a parent who suffered a hip fracture.

“This is landmark, in the sense that it could allow us to move on to more precise guidelines,” said Dr. Heidi Nelson, a researcher at the Oregon Health & Science University who is an expert on the topic. “It’s an expenditure of time, it’s exposure to radiation, and it’s cost. And there’s no reason to expose yourself to any risks if there’s going to be no benefit,” explained Dr. Virginia Moyer, who heads the U.S. Preventive Services Task Force, a government panel that issues testing guidelines.