Repeat bone mineral density testing 8 years after initial measurement does not improve the ability to predict fractures in healthy elderly women, according to Dr. Teresa A. Hillier and her associates.
Repeat BMD testing is done “commonly” in clinical practice, even though “there is little evidence evaluating the additional value of repeat BMD testing for fracture risk,” the investigators reported (Arch. Intern. Med. 2007;167:155–60).
The Study of Osteoporotic Fractures included 9,704 white women aged 65 years and older who were living in four regions of the United States. Of the women, 4,124 underwent initial BMD measurement in 1989–1990 and then had a repeat BMD measurement a mean of 8 years later, forming the sample for the current study, said Dr. Hillier of Kaiser Permanente Center for Health Research Northwest, Portland, Ore., and her associates.
The subjects were followed for an additional 5 years to track the incidence of fractures. The BMD measurements were taken at the proximal femur, intertrochanter, trochanter, femoral neck, and Ward's triangle. The 513 subjects who sustained a fracture between the initial and the repeat BMD assessments were excluded from the study.
Both measurements of BMD were significant predictors of hip fracture and nonspinal fracture risks. “Each standard deviation lower in either initial or repeat BMD was associated with a 55%–61% increased risk of incident nonspine fracture, a 102%–121% increased risk of incident hip fracture, and a 75%–86% increased risk of spine fracture,” Dr. Hillier and her associates reported.
However, the repeat BMD did not add to the overall predictive value for any type of fracture risk. These results persisted in subgroup analyses of women who used estrogen or bisphosphonate, compared with those who did not.
Their findings do not imply that repeat BMD measurement may not be useful for certain individual patients, “particularly if intervening clinical factors are present that would likely accelerate BMD loss greater than average,” Dr. Hillier and her associates noted.
“However, our results do suggest that, for the average healthy older woman…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,” they wrote, noting this study did not address BMD testing to monitor osteoporosis treatment response. These results may not be generalizable to men, nonwhite women, or women younger than 65.