Clinical Review

UPDATE ON OSTEOPOROSIS

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What we’ve learned about when to measure BMD and how to identify lesser-known causes of bone loss, as well as the value of quantitative ultrasound in determining the risk of fracture. And in the pipeline: a drug that curbs bone resorption without limiting bone formation.


 

HAVE YOU READ THESE OTHER ARTICLES ON BONE HEALTH?

What is the optimal interval for osteoporosis screening in postmenopausal women before fracture occurrence and osteoporosis?
Steven R. Goldstein, MD (Examining the Evidence, August 2012)

Update on Menopause
Andrew M. Kaunitz, MD (May 2012)

Update on Osteoporosis
Steven R. Goldstein, MD (November 2011)

An appeal to the FDA: Remove the black-box warning for depot medroxyprogesterone acetate?
Andrew M. Kaunitz, MD; David A. Grimes, MD (Guest Editorial, August 2011)

Osteoporosis is a significant health issue—and it is likely to remain so as more and more women live longer and longer. In fact, increasing age is the single biggest risk factor for osteoporotic fragility fracture.

Over the past year, important research has improved our understanding in diverse areas of bone health. In this Update, I highlight studies that:

  • seek to elucidate the optimal frequency of dual-energy x-ray absorptiometry (DXA) imaging to assess bone mineral density
  • review secondary causes of osteoporosis besides menopause-related estrogen deficiency
  • explore the use of quantitative ultrasound (QUS) to predict the risk of fracture
  • report on a new class of pharmaceutical agents that inhibit the bone-resorption enzyme Cathepsin K.

All of these issues are clinically relevant to the ObGyn specialty because, when it comes to our patients’ bone health, we often function as the primary care physician.

When is DXA indicated—and how often should it be repeated?

Gourlay ML, Fine JP, Preisser JS, et al; Study of Osteoporotic Fractures Research Group. Bone-density testing interval and transition to osteoporosis in older women. N Engl J Med. 2012;366(3):225–233.

Lewiecki EM, Laster AJ, Miller PD, Bilezikian JP. More bone density testing is needed, not less. J Bone Miner Res. 2012;27(4):739–742.

American Society for Bone and Mineral Research response to media coverage of New England Journal of Medicine study: “Bone density testing interval and transition to osteoporosis in older women” [press release]. http://www.asbmr.org/about/pressreleases/detail.aspx?cid=3801baff-0df3-47c0-874f-08a185d67001. Published February 1, 2012. Accessed October 15, 2012.

Recommendations from professional societies, such as the National Osteoporosis Foundation, the International Society of Clinical Densitometry, and the American College of Obstetricians and Gynecologists say virtually the same thing about DXA imaging: Screening is appropriate for women 65 years and older and for postmenopausal women younger than age 65 who have risk factors for fracture. Risk factors include:

  • history of a fragility fracture
  • body weight less than 127 lb
  • medical causes of bone loss, such as medication or disease
  • parental history of hip fracture
  • current smoker
  • alcoholism
  • rheumatoid arthritis.

The measurement of bone mineral density (BMD) has been the cornerstone of the diagnosis of osteopenia and osteoporosis since these classifications were introduced by the World Health Organization (WHO) in 1994. Although we are now able to evaluate a woman’s fracture risk using the FRAX tool, which does not require BMD assessment, DXA scanning has become entrenched in routine clinical practice in the United States. In addition, patients who use drugs to reduce their fracture risk often demand periodic testing to see how they are doing. Even women who do not take medications often want periodic assessment to confirm that they are not “losing bone.” Medicare allows for testing every 23 months.

23-month screening interval does not fit all women

Gourlay and colleagues prospectively followed 4,957 women aged 67 years or older who had no history of hip or vertebral fracture and who were not being treated for osteoporosis. After follow-up for as long as 15 years, investigators found that the better a woman’s initial bone density, the longer it took for her to develop osteoporosis. For example, among women over 67 years of age who had a T-score of –1.0 or better, it would take 16.8 years for 10% of this population to develop osteoporosis. In contrast, among women over 67 years of age who had a T-score of –2.0, it would take only 1.1 years for 10% of this population to develop osteoporosis.

This finding certainly calls into question the notion that all patients should be screened every 23 months. It may be better to think of screening as a way of triaging patients for decisions relative to subsequent follow-up.

Media distorted take-home message

This study was the focus of considerable attention from the media, which implied that too much DXA screening is being performed. In reality, only 13% of women over the age of 65 undergo a baseline DXA scan. However, routine follow-up of all patients at 23-month intervals is clearly not appropriate.

Because this study primarily involved white women older than age 67, extrapolation of its findings to other groups may not be appropriate. Nevertheless, the study helps to underscore the fact that reliance on BMD measurement alone should not be used to determine the need for therapeutic intervention. The FRAX tool can be used on an annual basis to assess a woman’s risk of fracture and does not require follow-up DXA imaging at any arbitrary interval.

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