TORONTO — Women aged 67 years or older with a bone mineral density T score higher than −1.50 on dual-energy x-ray absorptiometry can have their next DXA examination deferred for at least 10 years with a low risk that they'll progress to osteoporosis in the interim, according to an analysis of data from more than 5,000 U.S. women.
“Fewer than 10% of women with a BMD [bone mineral density] T score of more than −1.50 were estimated to transition to osteoporosis if followed for 15 years,” Dr. Margaret L. Gourlay said.
For these women, “repeat testing before 10 years is unlikely to show osteoporosis,” she said, and for women with a T score of −1.50 to −1.99, “a 5-year interval could be considered.”
The results provide the first evidence-based guidance available on the appropriate interval for osteoporosis screening in elderly women.
“The value of these results is that we can be less concerned about women with good BMD,” Dr. Gourlay said in an interview. “We don't need to go on autopilot and screen [all women] every 2 years.”
Medicare reimburses for screening women aged 65 years or older with dual-energy x-ray absorptiometry (DXA) every 2 years, she noted, and hence U.S. physicians often recommend this screening interval.
Earlier this year, however, an updated review of osteoporosis screening by the U.S. Preventive Services Task Force (USPSTF) noted that no evidence existed to support any screening interval (Ann. Intern. Med. 2010;153:99–111).
The results “were a surprise in a good way,” said Dr. Gourlay, a family physician at the University of North Carolina in Chapel Hill. “This is good news for women with good BMD. For women with higher bone density, we're probably doing some unnecessary testing.”
The new results also showed that the T score exerted the strongest influence on the osteoporosis screening interval, more so than clinical risk factors for fracture. Adjustment for “risk factors did not make too much of a difference, so physicians do not need to make a FRAX calculation” to decide a screening interval, she said. “They can just go by the BMD.”
“With FRAX [the World Health Organization's Fracture Risk Assessment Tool] you don't just look at BMD, but primary care physicians can't stop [in the middle of a patient consultation] to calculate a FRAX score,” Dr. Gourlay said.
“When a patient has a BMD result in the good range, the main value of the new results is that we can be less concerned about these women” and the need for rescreening in the near future, she noted.
“The importance [of the new findings] is not the absolute time estimates we found; it's the magnitude of the difference.
A 16-year interval [for 10% of women to develop osteoporosis] for women in the top two T score groups, and a 5-year interval [for women with a baseline T score of −1.50 to −1.99] is quite different” from the way most physicians practice today, she said.
She cautioned that the finding needs confirmation from similar analyses using different data sets, and that it remains up to health policy-setting groups, such as the USPSTF, to consider the findings and use them to formulate updated screening recommendations. But, she added, the findings have already influenced her own approach to handling screening intervals.
“If I have a patient who missed a test and her prior T score was more than −1.50, I'm not nearly as worried now,” said Dr. Gourlay.
The analysis used data collected in the Study of Osteoporotic Fractures (SOF), which enrolled women aged 65 years or older in four U.S. cities starting in 1986 and has followed them since then.
Dr. Gourlay and her associates focused on 5,036 women in the study who underwent at least two serial BMD measures over a total of 15 years. Patients were excluded from analysis if they had osteoporosis at any hip site at baseline, had an incident hip fracture, or were treated with a bisphosphonate or calcitonin. Patients also were excluded if they died or dropped out of the study.
The analysis included 1,275 women who had at least one normal baseline BMD value (a T score of −1.00 or greater) and 4,279 women with at least one T score that identified them as having osteopenia (−1.01 to −2.49).
Some women fell into both categories if they underwent at least three DXA examinations starting with at least one normal T score followed by at least one osteopenic score.
At baseline, the rate of estrogen use ran 25% in women with a normal T score at baseline and 16% in women with osteopenia – relatively high rates by today's standards but typical for practice in the 1980s.