Repeating a bone mineral density (BMD) scan up to eight years after an initial BMD appears to provide little additional benefit for predicting fractures among older postmenopausal women – Archives of Internal Medicine, JAMA/Archives journal.
BMD as measured by a method known as dual-energy x-ray absorptiometry helps physicians predict fractures and has become the gold standard for osteoporosis screening, according to background information in the article. Current guidelines recommend screening all women for osteoporosis using BMD measurements at age 65. However, there is little evidence supporting the use of repeat BMD testing for evaluating fracture risk, but such additional tests are commonly performed in clinical practice.
Teresa A. Hillier, M.D., M.S., of Kaiser Permanente Northwest/Hawaii, Portland, Ore., and colleagues measured total hip BMD in 4,124 older women (average age 72 years) in the Study of Osteoporotic Fractures between 1989 and 1990 and again an average of eight years later. The researchers calculated the rate of change in BMD and followed the women for an average of five years after the repeat BMD to see which women developed fractures. Participants were contacted by postcard every four months and fractures were verified through radiology reports and x-ray films.
During the follow-up period, 877 women had a non-traumatic non-spine fracture, including 275 hip fractures, and 340 women developed a spine fracture. On average, the women’s initial BMD measurements were low–compared to young women–but not in the osteoporotic range; the group lost an average of .59 percent of their bone mass per year between examinations. “In each of the four BMD models (initial BMD, repeat BMD, change in BMD between the two examinations, and initial BMD plus change in BMD), BMD was a significant predictor of incident non-spine and hip fracture risk, and was associated with morphometric spine fractures,” fractures in which the diagnosis is made based on vertebral shape, the authors write.
In the study, “we did not find any improvement in the overall predictive value ? in a second measure of BMD, obtained a mean [average] of eight years later, in prediction of hip, spine or overall non-spine fracture risk,” they continue. “In other words, the initial BMD was highly, and similarly, predictive of fracture risk in our population.”
Despite these findings, a repeat BMD measurement might still be useful in some women, including those with clinical factors that contribute to rapid bone loss and younger women in early menopause. “However, our results do suggest that, for the average healthy older woman 65 years or older, a repeat BMD measurement has little or no value in classifying risk for future fracture–even for the average older woman who has osteoporosis by initial BMD measure or high BMD loss,” the authors conclude.