Repeat Bone Density Tests Questioned

Repeat bone mineral density (BMD) testing in older men and women may not improve the ability to predict fractures beyond the insight gained from the original bone scan, researchers report. The study was conducted because screening for osteoporosis with BMD is recommended for older adults, and it was unclear whether repeating a BMD screening test improves fracture risk assessment.

In a population-based cohort of older men and women not yet treated for bone loss, the result of a second bone density test within four years of the first did not “meaningfully improve” fracture prediction, according to Sarah Berry, M.D., and her colleagues at the Institute for Aging Research at Hebrew SeniorLife in the Boston, Mass., suburb of Roslindale.

The finding suggests that repeated bone scans might not be needed, at least among people at relatively low risk for fractures, Berry and her colleagues argued in the Journal of the American Medical Association article.

Murray Favus, M.D., of the University of Chicago (Ill.) said doctors must analyze the study population to determine whether the findings apply to any particular patient. “This is not a generalized recommendation that is going to fit all people,” he told MedPage Today.

An initial BMD test plays an important role in managing osteoporosis, the authors noted. For instance, guidelines for starting drug therapy for osteoporosis are based on bone density combined with risk classification scores but it’s not clear if repeated testing has any value, and the interval that is most effective is not known.

Nevertheless, Medicare pays for a bone density screening every two years without limitation on the number of tests and regardless of the baseline bone density.

If bone density tests are not helpful in managing patients, then clinicians have an opportunity to save money, the researchers contended. To prove their point, they examined the Framingham Osteoporosis Study, whose participants were enrolled starting in 1948. From 1987 through 1999, living participants were invited for three BMD tests, about four years apart.

For this analysis, Berry and colleagues looked at 310 men and 492 women with an average age of 74.8 who had two measurements of femoral neck bone density and followed them from the second measure until death or through 2009 or 12 years of follow-up.

The primary outcome of the study was the risk of hip or some other major osteoporotic fracture.
After a median follow-up of 9.6 years, Berry and colleagues found, 113 participants (14.1 percent) met the primary endpoint, with 88 hip, 24 spine, five shoulder, and 33 forearm fractures. The average change in BMD was a drop of 0.6 percent annually, ranging from a gain of 5.6 percent to a loss of 9 percent per year.

In a model adjusted for clinical characteristics and baseline bone density, every standard deviation of decrease in annual percentage bone density change was associated with a hazard ratio for incidence hip fracture of 1.43, with a 95 percent confidence interval from 1.16 to 1.78.

At 10 years’ follow-up, the absolute risk of hip fracture was 10.2 percent among participants whose bone density change was average, compared with 14.1 percent among those whose change was a standard deviation below the mean.

Similarly, every standard deviation decrease in annual percentage annual percentage bone density change was associated with a hazard ratio of 1.21 for major osteoporotic fractures (with a 95 percent confidence interval from 1.01 to 1.45).

Again, at 10 years’ follow-up, participants with an average change had an absolute risk of major osteoporotic fracture of 15.6 percent, compared with 18.3 percent among those whose change was a standard deviation lower.

Despite those significant associations, Berry and colleagues found, there was little difference in the area under the receiver operating curve—a measure of predictive value—for models based on baseline bone density or percentage change over time.

Combining baseline bone density and change over time also did not change the area under the curve, they reported.

The study concluded summarily that in untreated men and women of mean age 75 years, a second BMD measure after four years did not meaningfully improve the prediction of hip or major osteoporotic fracture. Repeating a BMD measure within four years to improve fracture risk stratification may not be necessary in adults this age untreated for osteoporosis.

The National Osteoporosis Foundation states that BMD tests can help patients learn if they have opsteoporosis before they break a bone, predict the likelihood of breaking a bone, and monitor the improvement or decline of bone density. It currently recommends that women over 65 and men over 70 should get BMD tests, as well as other at-risk populations.