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

However, too much of anything can be bad. Excessive exercise that leads to amenorrhea can cause bone loss that is not fully recoverable, thus increasing the risk for stress fractures and fractures of the hip and spine. Since the prevalence of amenorrhea in female athletes ranges from 10% to 45%, this is a significant nonmenopause-related risk factor for osteoporosis.¹¹

The clinician needs to inquire specifically about exercise levels and menstrual patterns.

PITFALL #4Failing to ask about medications or diseases

Another common cause of osteoporosis is long-term use of certain systemic agents.

Glucocorticoids directly affect bone by limiting formation and increasing resorption. They also impair the body’s ability to absorb calcium from the intestine and increase renal excretion of the mineral. At high doses—ie, 7.5 mg per day or more of prednisone or the equivalent—bone loss can reach 10% within 1 year.¹²

Other drugs to watch for include anticonvulsants, especially phenytoin and phenobarbital,¹⁰ intramuscular medroxyprogesterone acetate, tamoxifen (premenopausal),¹ and thyroxine, especially when daily doses exceed 200 mg,¹² as well as the other agents listed in TABLE 2.

Diseases. Among conditions associated with osteoporosis are AIDS/HIV, depression (and other conditions that limit mobility), eating disorders, and thyrotoxicosis (TABLE 2). A thorough evaluation for osteoporosis should include consideration of these entities.

PITFALL #5Measuring the wrong site

Is the hip, spine, or another site best for measuring bone density? The issue is particularly relevant because of rapid proliferation of portable, low-cost, peripheral bone-measuring devices in some practices—even in shopping malls. This device makes evaluation of a single peripheral skeletal site quite simple. However, peripheral BMD is a better indicator of cortical than trabecular bone density, and may inadequately evaluate spinal bone status.

The gold standard for BMD measurement is the central DXA tabletop machine, which makes it possible to measure multiple skeletal sites, if necessary. In fact, the WHO based its criteria on this standard.

If this technology is not available, the hip is the preferred site, especially in women over 60. The reason? Degenerative osteoarthritic spinal calcifications in older women can give falsely elevated BMD values. In contrast, in early menopause, spinal measurements may be useful, since bone is more rapidly depleted from the spine than from the proximal femur at this stage.¹³

Hip measurement is the best predictor of hip fractures, and usually predicts fractures at other skeletal sites as well.¹

As for the experts’ opinions, the NOF recommends measuring the hip, AACE suggests the spine and proximal femur, and NAMS recommends the total hip, femoral neck, or spine.^1,14-16

In my practice, when DXA is used, I prefer to measure the spine and femoral neck at a minimum. If there is a spinal deformity or another confounder, I obtain a forearm measurement.

PITFALL #6Relying on bone density measurement alone

Although T and Z scores offer insight about a woman’s bone density, they are not definitive measures of the fracture risk. For example, even when a 50-year-old woman and a 75-year-old woman have the same BMD, the older woman is far more likely to experience an osteoporotic fracture.¹⁷ The greater propensity for falls among the elderly may partially explain this difference, but does not account for all of it. Obviously, there are other markers of risk besides BMD.

The take-home message is that, when estimating fracture risk, don’t rely on bone densitometry alone. Rather, combine it with a thorough assessment of the patient’s history and risk factors.

Nevertheless, bone-densitometry measurements are vital. They can establish a baseline of bone density that is helpful for monitoring progress with therapy.

If a patient with a low-trauma fracture is found to have normal bone density, some other cause of the bone deterioration must be sought.

Clinical recommendations

TABLE 2 lists risk factors for postmenopausal osteoporosis. If a woman under 65 years presents with any of these factors, screening should be considered.¹⁰

TABLE 3 lists the screening guidelines of ACOG, NAMS, and other organizations.

Appropriate screening is an important tool that must be customized to the patient. In my practice, I discuss the risks and benefits of each option with the patient and we decide together whether screening should be performed.

As a gynecologist, I am most familiar with the ACOG and NAMS screening guidelines. However, I consider it important to be familiar with all the major recommendations, since other physicians who also care for our patients may be using these other guidelines.

Dr. Chervenak reports that she serves on the speaker’s bureau for Berlex, Pfizer, and Wyeth, on the advisory boards of Berlex and Pfizer, and has received grant support from Albert Einstein College of Medicine, American College of Obstetricians and Gynecologists, Berlex, Pfizer, and Solvay.