Osteoporosis Testing

Do Older Women Really Need Osteoporosis Testing Every Two Years?

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While many women older than 65 years are referred for bone mineral density (BMD) testing every two years, a new study published in the New England Journal of Medicine suggests that the interval can safely be much longer.[1] Bone mineral density is measured using the dual-energy x-ray absorptiometry (DXA) test, which generates a T-score—the number of standard deviations above or below the mean for a healthy 30-year-old woman who is the same ethnicity as the patient.

Although current guidelines recommend routine BMD screening scans for women 65 years of age or older, these guidelines are not based on evidence from longitudinal cohort studies. And in 2011, the U.S. Preventive Services Task Force (USPSTF) stated that although a minimum of two years is probably required to reliably measure changes in BMD, longer intervals may be necessary.[2] Osteoporosis affects more than 10 million Americans older than 50, including half of all postmenopausal women at some point, according to the National Osteoporosis Foundation.[3]

A U.S. research team studied 4,957 women who were at least 67 years old with a normal or lower-than-normal BMD (osteopenia) and followed their skeletal status for up to 15 years. None of the women had a history of hip or vertebral fracture or had been treated for osteoporosis. All women underwent BMD testing when they entered the study. The primary outcome measures were the estimated amount of time it took for 10% of the women to make the transition from normal BMD or osteopenia at baseline to osteoporosis before a hip or clinical vertebral fracture occurred and before treatment for osteoporosis was initiated. The goal was to determine how often screening would be necessary to catch the first signs of osteoporosis while, at the same time, avoiding over testing.

The women were divided into three risk groups based on their T-scores: high-risk (T-scores -2.49 to -2.0), moderate-risk (T-scores -1.99 to -1.5), and low-risk (T-scores of -1.49 and higher). Among the low-risk women, less than 1% developed osteoporosis over the next 15 years. For the moderate-risk women, the rate was less than 5% over the same time interval. Among the highest risk women, however, 10% progressed to osteoporosis in about a year. Within each given T-score range, younger women took longer to transition from osteopenia to osteoporosis; as well, women taking estrogen at baseline took longer to transition to osteoporosis compared with women who had taken estrogen in the past or never taken it.

The authors believe that the T-score is the best indicator of an appropriate BMD interval and that their findings will help clinicians make evidence-based decisions about how often women should be tested. As less than 1% of women with a normal T-score at baseline developed osteoporosis over 15 years, this should provide you with some assurance that for these women, BMD testing can be pushed out much farther than the current two years. As each screening test costs about $250 and can lead to false positives and unnecessary use of medications, these data are an important tool to help clinicians make health screening decisions that are based on evidence, rather than marketing, advocacy, and public beliefs.

But even if guidelines based on these data are adopted, you’ll still need to remain flexible in advising your patients as to the optimal testing interval. A woman with a normal T-score who then develops cancer and loses a lot of weight, for example, may be more vulnerable to developing osteoporosis and therefore may need to get screened before the 15-year interval. And women on the borderline of normal may also need to be screened more frequently, since they may cross over into moderate risk well before their next scheduled test.

Jill Shuman, MS, ELS
Published January 31, 2012

References

  1. Gourlay ML, Fine JP, Preisser JS, et al. Bone-density testing interval and transition to osteoporosis in older women. N Engl J Med. 2012;366(3):225-233.
  2. Screening for osteoporosis: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2011;154(5):356-364.
  3. National Osteoporosis Foundation. Clinician’s Guide to Prevention and Treatment of Osteoporosis.Washington, DC: National Osteoporosis Foundation; 2010.