Chapter 2-10: Osteoporosis Screening

What is the burden of disease?

1. In the United States, about 10.3 million people over the age of 50 have osteoporosis (15.4% of women and 4.3% of men).

2. The prevalence of osteoporosis is 25% in women aged 65 or older and 5.6% in men aged 65 or older.

3. More than 2 million fractures per year are related to osteoporosis, including about 300,000 hip fractures and 700,000 vertebral fractures.

4. Mortality rate in the first year after hip fracture is 20%.

Is it possible to identify a high-risk group that might especially benefit from screening?

1. Low BMD itself is the strongest risk factor for fracture.

2. Increasing age is the strongest risk factor for low BMD; other risk factors include low body weight (< 132 pounds), lack of hormone replacement therapy use, family history of osteoporosis, personal history of fracture, ethnic group (white, Asian, Hispanic), current smoking, 3 or more alcoholic drinks/day, long-term corticosteroid use (≥ 5 mg of prednisone daily for ≥ 3 months).

3. The WHO Fracture Risk Algorithm (FRAX) calculates the 10-year probability of hip or major osteoporotic fracture using femoral neck BMD and clinical risk factors (available at http://www.shef.ac.uk/FRAX/).

   1. Although the full FRAX algorithm incorporates femoral neck BMD, it is possible to input just clinical risk factors to estimate the patient’s clinical risk.

   2. Using just clinical risk factors, a 65-year-old woman with no additional positive answers has a 9.3% 10-year risk for any osteoporotic fracture.

4. The Osteoporosis Self-Assessment Tool (OST) is designed to identify individuals more likely to have low BMD.

   1. OST score = [weight (kg) – age (years)] × 0.2

   2. Patients with a score of < 2 are considered high risk.

5. For identifying osteoporosis (T score ≤ –2.5), the FRAX has a sensitivity of 33.3% and specificity of 86.4% (LR+, 2.4; LR–, 0.77); the OST has a sensitivity of 79.3% and a specificity of 70.1% (LR+, 2.6; LR–, 0.29).

What is the quality of the screening test?

1. Background

   1. Can measure bone density with a variety of methods (dual-energy x-ray absorptiometry, single-energy x-ray absorptiometry, ultrasonography, quantitative CT) at a variety of sites (hip, lumbar spine, heel, forearm)

   2. Current bone density is compared with peak predicated bone density and then reported as number of SD above or below peak predicted bone density.

   3. Osteoporosis is defined as a bone density “T score” at least 2.5 SD below peak predicted bone density (T score = –2.5 or more negative).

   4. Osteopenia is defined as a T score between –1.0 and –2.5.

   5. Normal is within 1 SD of peak predicted bone density.

2. Dual-energy x-ray bone absorptiometry is the gold standard test.

   1. Has been shown to be a strong predictor of hip fracture risk; femoral neck is best site to measure.

   2. The relative risk of hip fracture is 2.5 for each decrease of 1 SD in bone density at the femoral neck.

   3. The relative risk of vertebral fracture is 1.9 for each decrease of 1 SD in bone density at the femoral neck.

3. There are limited data regarding the optimal interval between ...