Case Study

PK, a 65-year-old black woman, comes to get her annual influenza vaccination. She says she appreciates your recent visit to her mother, who is recovering from surgery following a hip fracture. PK asks if she should be screened for osteoporosis. She is healthy, weighs only 125 lb (57 kg) at 5 feet 5 inches, and takes calcium supplements with vitamin D but no estrogen therapy.

Case Study Questions

1. Which of the following characteristics put PK at increased risk for osteoporosis?

• A. Race.

• B. Weight.

• C. Not taking estrogen therapy.

• D. Age.

2. You review the U.S. Preventive Services Task Force (USPSTF) recommendations on screening for osteoporosis in postmenopausal women before advising PK. Which one of the following statements about the USPSTF recommendations is correct?

• A. The USPSTF recommends routine osteoporosis screening in women 50 years and older.

• B. The USPSTF recommends routine osteoporosis screening in women 65 years and older.

• C. The USPSTF does not recommend for or against routine osteoporosis screening in women.

• D. The USPSTF recommends against routine osteoporosis screening in women.

• E. The USPSTF recommends osteoporosis screening only in women who are at increased risk for osteoporotic fractures.

3. Which one of the following statements about osteoporosis screening instruments is correct?

• A. Dual-energy x-ray absorptiometry (DEXA) cannot identify post-menopausal women who have a higher short-term risk for fracture.

• B. The likelihood of being diagnosed with osteoporosis is not affected by the brand of densitometer used.

• C. The likelihood of being diagnosed with osteoporosis is not affected by the type of screening test used.

• D. Peripheral bone density testing has been proved to be as effective as DEXA.

• E. Bone density measured at the femoral neck by DEXA is the best predictor of hip fracture.

Answers

1. The correct answers are B, C, and D. Age is the strongest predictor of osteoporosis. In one large study, women aged 65 to 69 years had 5.9-fold higher odds of having osteoporosis compared with women 50 to 54 years of age; women 75 to 79 years of age had 14.3-fold higher odds compared with women 50 to 54 years of age. Low body weight (i.e., less than 154 lb [70 kg]) or body mass index and not taking estrogen therapy also are consistently associated with osteoporosis, but to a lesser degree than age. However, low body weight is the best predictor of low bone mineral density. Other risk factors for fracture or low bone density found in some, but not all, studies include personal history of fracture, family history of osteoporotic fracture, low levels of physical activity, smoking, excessive alcohol or caffeine use, and low levels of calcium and vitamin D intake. The prevalence of osteoporosis in African-American women is about one half that of women of other groups. Clinicians can assess osteoporosis risk with validated instruments such as the three-item Osteoporosis Risk Assessment Instrument and the six-item Simple Calculated Osteoporosis Risk Estimation tool.

2. The correct answer is B. The USPSTF recommends that women 65 years and older be screened routinely for osteoporosis. For women at increased risk, the USPSTF recommends beginning screening at age 60. The USPSTF found good evidence that screening for osteoporosis accurately predicts short-term fracture risk (i.e., within one year) and that treating asymptomatic women reduces their risk. No study has evaluated the optimal interval for repeated screening, and there are no data to determine the appropriate age to stop screening. A minimum of two years may be needed to reliably measure a change in bone mineral density, but a longer interval may be adequate for repeated screening to identify new cases of osteoporosis.

3. The correct answer is E. Bone density measured at the femoral neck by DEXA is the best predictor of hip fracture and is comparable to forearm measurements for predicting fractures at other sites. Several other radiologic methods are used to measure bone density at peripheral sites. The likelihood of being diagnosed with osteoporosis varies greatly depending on the site and type of bone measurement test, the number of sites tested, the brand of the densitometer, and the relevance of the reference range. Peripheral bone density testing has shown the ability to identify patients at short-term risk for fracture, but further research is needed to determine how this technique compares with DEXA.