Clinical Review

Who is at risk of fracture? Avoid 6 pitfalls of osteoporosis screening

OBG Manag. 2003 November;15(11):54-62

Easily misunderstood symptoms, overlooked history and lifestyle clues, mistaken choice of densitometry site and method—these and other snags can trip up efforts to screen patients adequately and start intervention early.

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References

1. Physician’s Guide to Prevention and Treatment of Osteoporosis. Washington, DC: National Osteoporosis Foundation; 2003. Available at: www.nof.org/professionals/clinical/clinical.htm Accessed October 8, 2003.

2. Melton LJ, III, Chrischilles EA, Cooper C, et al. How many women have osteoporosis? J Bone Miner Res. 1992;7:1005-1010.

3. Melton LJ, III. Epidemiology of fractures in North America. In: Christiansen C, Overgaard K, eds. Osteoporosis. Copenhagen, Denmark: Osteopress APS; 1990(1);36-41.

4. Looker AC, Wahner HW, Dunn WL, et al. Updated data on proximal femur bone mineral levels of US adults. Osteoporosis Int. 1998;8:468-489.

5. Melton LJ, III. Epidemiology of hip fractures: implications of the exponential increase with age. Bone. 1996;18(3 Suppl):121S-125S.

6. Nguyen TV, Maynard LM, Towne B, et al. Sex differences in bone mass acquisition during growth: the Fels Longitudinal Study. J Clin Densitom. 2001;4:147-157.

7. ISCD clinical track syllabus version 5 2, Sept 18, 2002:30-31 (JL Chervenak, MD).

8. Wasnich RD, Ross PD, Vogel JM, et al. Osteoporosis: Critique and Practicum. Honolulu, HI: Banyan Press; 1989;179-213.

9. Miller PD, Canalis E, Gass MLS. Osteoporosis: a new era in recognition and treatment. Annenberg Center for Health Sciences at Eisenhower; 2003. Available at: www.medscape.com/viewprogram/2664_pnt Accessed October 8, 2003.

10. Management of postmenopausal osteoporosis: position statement of the NAMS. Menopause. 2002;9:84-101.

11. A decision tree for the use of ERT/HRT in postmenopausal women: consensus opinion of the NAMS. Menopause. 2000;7:76-86.

12. Osteoporosis Task Force AACE 2001 medical guidelines for clinical practice for the prevention and management of postmenopausal osteoporosis. Endocr Pract. 2001;7:293-312.

13. American College of Obstetricians and Gynecologists. Committee Opinion #270: Bone Density Screening for Osteoporosis. Washington, DC: ACOG; March 2002.

14. NIH Consensus Development Panel on Osteoporosis Prevention Diagnosis and Therapy. Osteoporosis prevention, diagnosis, and therapy. JAMA. 2001;285:785-795.

15. Menopause Core Curriculum Study Guide. 2nd ed. Mayfield Heights, Ohio: North American Menopause Society; 2002. Available at: www.menopause.org/edumaterials/studyguide/studyguide.html Accessed October 8, 2003.

16. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Fact Sheet: Exercise and Bone Health. Washington, DC: NIH;2001. Available at: http://health.nih.gov/result.asp?disease_id-1161 Accessed October 9, 2003.

17. American College of Obstetricians and Gynecologists. ACOG Educational Bulletin #246: Osteoporosis. Washington, DC: ACOG; 1998.

KEY POINTS

Dual-energy x-ray absorptiometry is the gold standard for bone density measurement.
Don’t rely on bone densitometry alone to estimate fracture risk; combine it with thorough assessment of history and risk factors. Nonetheless, bone densitometry is vital, and can establish a baseline that is useful for monitoring therapy.
When interpreting densitometry results, base the diagnosis on the lowest score obtained.
Over her lifetime, a woman’s risk of hip fracture is greater than her risk of breast, endometrial, and ovarian cancer combined.

Osteoporosis has claimed the spotlight. The sheer volume of information published in recent years is astounding. From clinical guidelines to mainstream media, the message is clear: Osteoporosis can be prevented and effectively treated if intervention is early enough. The key? Proper screening of women who may be at risk.

That’s where the difficulty begins. Amid a profusion of data, the simple how-to—and when-to—of screening can get lost. But osteoporosis is a potent threat. Over her lifetime, a woman’s risk of hip fracture is greater than her risk of breast, endometrial, and ovarian cancer combined. Since many women are discontinuing hormone replacement therapy in the aftermath of the Women’s Health Initiative, the risk seems likely to increase.

This article describes a sensible screening strategy focusing on 6 common pitfalls. Many observations come directly from the clinical setting—specifically, a practice in reproductive endocrinology with special interest in the health-care needs of maturing women.

Scope of the problem

As the National Osteoporosis Foundation (NOF) observes, osteoporosis is a “silent disease until it is complicated by fragility fractures.”¹ It affects people of all ages and races, but is most prevalent among postmenopausal white and Asian women. However, even African-American and Hispanic women face a heightened risk.^2-4

One of every 2 white women will experience an osteoporotic fracture.¹ In fact, after age 65, the incidence of hip fracture in white women is greater than the incidence of stroke, diabetes, or breast cancer.⁵

If a hip fracture occurs, the mortality rate within the first year is 10% to 20%.^1,6 One third of hip-fracture patients break the opposite hip, and only 40% regain their previous level of mobility.¹

For survivors and their loved ones, the diminished quality of life and loss of independence can be devastating. Not surprisingly, many patients also experience psychological symptoms such as depression.

Vertebral fractures are another dire consequence of osteoporosis, causing back pain, loss of height, kyphosis, and even death.

The economic burden of osteoporosis is no less daunting. In 1995, osteoporotic fractures were the “presumed cause” of 180,000 nursing home admissions, more than 430,000 hospital admissions, and roughly 2.5 million doctor visits.¹ Each year these fractures cost about $17 billion in health care—or $40,000 per hip fracture.¹

Measuring bone density: The basics

Dual-energy x-ray absorptiometry (DXA) is the gold standard for bone-density measurement. It is recommended by the American Association of Clinical Endocrinologists (AACE), the American College of Obstetricians and Gynecologists (ACOG), and the North American Menopause Society (NAMS). Quantitative computed tomography is also recommended by the AACE.

Quantitative ultrasound, which is gaining in popularity, can yield information on bone structure and elasticity in peripheral locations such as the heel, patella, and tibia. It lacks the ionizing radiation of DXA.

It is important for the clinician to be familiar with all these modalities, though the ultimate selection will vary from patient to patient.

Contraindications to densitometry include pregnancy. While the risk during gestation is negligible, it still exceeds potential benefits.

Limitations. A patient who has undergone recent gastrointestinal studies and nuclear medicine tests should wait at least 72 hours before having a central DXA scan.

Morbid obesity may limit the options, since the weight limit of most central DXA scanners is 250 to 350 lb. Check with the manufacturer for machine limitations and obtain a forearm measurement if necessary.

A family history of osteoporosis, particularly in the patient’s mother or another first-degree relative, is a good predictor of the disease.

Orthopedic instrumentation may interfere with measurement at some sites.⁷

T and Z scores. Osteoporosis is defined by comparing the patient’s bone density to 2 different populations: her own age group and young adults.

When bone density is compared to that of her own age group, the result is conveyed as a “Z” score, which represents the number of standard deviations away from the mean.
When it is compared to the peak bone mass of a “normal” young adult, the result is given as a “T” score—again, the number of standard deviations away from the mean. The World Health Organization (WHO) defines osteoporosis as a T score at or below –2.5 (TABLE 1).