But there has been no consensus about how frequently BMD screenings are needed in order to not miss opportunities to prevent fractures. Some providers recommend repeat screenings every one to two years. A recent study, published in the New England Journal of Medicine, investigated this issue.
The study followed almost 5,000 women for 15 years to determine how rapidly women with normal BMD or with osteopenia progressed to a stage where treatment to prevent fractures was indicated. They researchers wanted to determine how the BMD testing interval related to the timing of the transition from normal BMD or osteopenia to the development of osteoporosis before a hip or clinical vertebral fractures occurs.
The study looked at 4,967 women who were 67 years or older and who did not have osteoporosis at the start. Some of the women had normal bone densities and some had mild, moderate, or advanced osteopenia. They followed them for 15 years to determine how long it took each group to get to the point where they developed osteoporosis so significant as to be at enough risk for bone fracture that they would warrant treatment.
The investigators reasoned that information about the pace or progression of the stages of normal or early bone thinning to clinically significant osteoporosis could help inform decisions about the appropriate intervals for retesting patients.
Based on the rates of transition from osteopenia to osteoporosis in the four groups -- normal BMD, mild, moderate, or severe osteopenia -- the researchers recommended that women whose initial tests show normal BMD or mild osteopenia can wait 15 years for follow up. Those with moderate osteopenia can wait five years, and those with advanced osteopenia should wait only one year between tests.
The researchers found that the women with the least osteopenia at the outset of the study took the longest to progress to clinically significant osteoporosis. They also found that within each category of osteopenia, the younger women progressed more slowly to osteoporosis than the older women. The transition time to osteoporosis was longer for women who were taking estrogen at the start of the study as compared with women who had taken estrogen before the study began or had never taken it at all.
The researchers maintain that the baseline T-score is the most important factor to consider when choosing how frequently to repeat the BMD test. But they note there may be compelling reasons to screen more often. Clinicians may elect to increase the frequency of screenings if there are additional risk factors that would suggest a faster progression of bone loss such as decreased activity or mobility, or significant weight loss.
They also note that the expected time to osteoporosis is less in the very elderly and that screening every three years instead of every five years might be considered for women who are older than 85 years and have moderate osteopenia.