Performing a second bone mineral density measurement 4 years after an initial measurement was "of little value" in refining the estimation of fracture risk in osteoporosis, according to a report published online Sept. 24 in JAMA.
The finding calls into question the current practice of performing serial bone mineral density (BMD) tests at even shorter 2-year intervals to enhance fracture risk assessment, the study investigators noted.
In a secondary analysis of data from the Framingham Osteoporosis Study, BMD change during a 4-year interval "provided little additional information beyond baseline BMD for the clinical management of osteoporosis," said Dr. Sarah D. Berry of the Institute for Aging Research, Hebrew SeniorLife, Boston, and her associates (JAMA 2013;310:1256-62).
The appropriate interval between BMD assessments remains controversial, and studies of the issue have yielded mixed results.
Studies that reported a strong association between BMD loss during a short interval and subsequent fractures typically focused on the small subgroup of patients who had accelerated bone deterioration. Other studies primarily involving patients with low or normal bone loss have reported only a weak association between BMD loss and later fractures, the investigators said.
To determine whether repeat BMD testing is useful, Dr. Berry and her colleagues examined the rate of hip and major osteoporotic fracture among 310 men and 492 women in the prospective, population-based Framingham cohort.
The study patients underwent an initial BMD test of the femoral neck in 1987-1999, at a mean age of 74.8 years. None was receiving treatment for osteoporosis at that time. The patients then had at least one repeat BMD test a mean of 3.7 years later (range, 2.4-6.0 years later). The study participants then were followed for approximately 12 years or until they died.
During follow-up, 113 study patients (14.1%) had one or more major osteoporotic fractures. There were 88 hip, 24 spine, 5 shoulder, and 33 forearm fractures.
BMD loss during the interval between the first and second BMD assessments was associated with subsequent fracture. However, assessment of such loss provided little clinical value beyond that of the initial BMD test.
"The second BMD measure resulted in a small proportion of individuals [being] reclassified as [at] high risk of hip or major osteoporotic fracture," Dr. Berry and her associates said. But it remains unclear whether such a small number of reclassifications justifies the current practice of performing repeat BMD tests every 2 years, they added.
"We conclude that repeating a BMD test after 4 years would rarely change the clinical management of osteoporosis based on risk scores of hip fracture," the researchers explained. "Individuals with the greatest changes in risk scores were those who would have already been classified at high risk based on [the initial] BMD and [their] clinical characteristics."
Although some experts suggest that short rescreening intervals are warranted in high-risk patients, "we found no difference in the association between BMD change and fracture when stratified by sex, age, BMI, weight loss, T score, or fracture risk score," the study authors noted.
"Despite our findings, we recognize that detecting BMD loss would have been paramount for the small numbers of individuals reclassified by a second BMD test who went on to experience a fracture," Dr. Berry and her colleagues said. For those patients, a repeat screening test would allow physicians to give osteoporosis medications and reduce fracture risk, even among patients 75 years or older.
However, for the clear majority of patients who show normal or only mild bone loss at an initial screening, further study is needed to predict which patients are likely to transition to high risk of fracture and would therefore benefit from repeat BMD testing.
The study was limited in that almost all the patients were white. The usefulness of repeated BMD screening might be different in other racial and ethnic populations, the investigators said.
The National Institutes of Health, the National Heart, Lung, and Blood Institute, and the Friends of Hebrew SeniorLife supported the study. Dr. Berry reported no relevant financial conflicts of interest; one of her associates reported ties to Amgen, Ammonett Pharma, Eli Lilly, Hologic, Merck Sharpe & Dohme, Novartis, and Roche.