Two-year bone density screening may be unnecessary for women with normal T-scores

Issue: March 2011

Since 2002, the US Preventive Services Task Force has recommended that women aged 65 years and older be routinely screened for osteoporosis and has suggested that a 2-year screening interval might be appropriate. However, what length the screening interval should be is a topic that remains controversial and undecided, with no definitive scientific evidence to provide guidance.

Now, a study led by Margaret L. Gourlay, MD, MPH, of the University of North Carolina (UNC) at Chapel Hill School of Medicine, finds that women aged 67 years and older with normal BMD scores may not need a repeat screening for 10 years.

“If a woman’s bone density at age 67 is very good, then she doesn’t need to be re-screened in 2 years or 3 years, because we’re not likely to see much change,” Gourlay said in a press release. “Our study found it would take about 16 years for 10% of women in the highest bone density ranges to develop osteoporosis.”

Gourlay, an assistant professor in UNC’s department of family medicine, presented these results at the annual meeting of the American Society for Bone Mineral Research in Toronto.

In the study, Gourlay and her colleagues analyzed data from 5,035 women aged 67 years and older that were collected as part of the longest-running osteoporosis study in the United States — the Study of Osteoporotic Fractures. The women were enrolled in the study from 1986 to 1988 and had BMD testing starting about 2 years later. All had BMD testing at least twice during the study period; some were tested up to five times during a period of 15 years.

For the analysis, women were categorized by BMD T-scores, which compare a person’s BMD to the expected bone density of a healthy young adult. Women with osteoporosis were excluded from the study.

The remaining women were placed in three groups according to their baseline BMD T-scores at the hip. Women in the high-risk group had T-scores ranging from –2.49 to –2, while those in the moderate-risk group had T-scores from –1.99 to –1.5. The low-risk group included two T-score ranges: T-scores –1.49 to –1.01, and normal BMD (those with T-scores of –1 or higher).

The researchers calculated estimated times for 10% of the women in each T-score group to transition to osteoporosis. For the high-risk group, the estimated time was 1.26 years, while it was about 5 years for the moderate-risk group and 16 years for the low-risk group.

The study concluded that baseline BMD is the most important factor for doctors to consider in determining how often a patient should be screened. It also suggests that older postmenopausal women with a T-score of –2 and below will transition to osteoporosis more rapidly, while women with T-scores higher than –2 may not need screening again for 5 to 10 years.

“Doctors may adjust these time intervals for a number of reasons, but our results offer an evidence-based starting point for this clinical decision,” Gourlay said.

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