Forearm densitometry: room in primary care practice for BMD tests.
"A single site measurement probably suffices for yes/no intervention decisions. You do just as well with forearm--if that is [the type of measurement] you have in your office--as any other single site," Dr. Michael Kleerekoper said.
Primary care physicians can use the smaller, peripheral dual x-ray absorptiometry (DXA) devices to determine if further work-up is warranted. Multiple sites are still neeeded for diagnosis of osteoporosis, but a single bone density assay is appropriate for screening. Also, forearm or heel devices are easier to use and more accurate than a blood pressure reading, said Dr. Kleerekoper, associate chair of internal medicine and director of bone and mineral metabolism and gerontology research at Wayne State University, Detroit.
"A lot of osteoporosis can be managed by a primary care physician in his or her office, and not everyone needs the sophisticated technology or the expense," he said. "It is the same as with diabetes--there are not enough specialists to treat, so it is treated in primary care offices."
But there are limitations to bone mineral density testing using smaller, portable DXA devices. For example, peripheral measures are not appropriate for follow-up or monitoring of responses to antiresorptive therapy. And assessment of risk fracture in older women (over age 70) is still better with a hip DXA scan.
Convenient and low-cost peripheral devices may be more appropriate for primary care offices, compared with the larger, more dedicated equipment that is required for hip or whole body scans, Dr. Kleerekoper said. Yet "most internists refer because the people who own the big machines tell them the little machines are no good. If you make a living doing hip and spine DXA, you will not be in a rush to promote other technologies."
Certain patient populations can benefit in particular from forearm measurements, including people with breast cancer, hyperthyroidism, or hyperparathyroidism.
In a case-control study of more than 200 newly diagnosed breast cancer patients, the cancer was associated with a proximal radius DXA Z-score greater than 1 (odds ratio, 1.98). The study included 50% white women and 50% black women. The association was independent of menopause status, age, body mass index, and use and duration of hormone therapy (Osteoporos. Int. [Epub ahead of print], Feb. 4, 2004).
Peripheral DXA also can identify patients with hyperthyroidism or hyperparathyroidism, because excess thyroid hormone has a preferential effect on the distal forearm bone. Dr. Kleerekoper routinely scans patients at the spine, hip, and forearm. If the forearm has the lowest T score, he notes on the report that the referring physician should consider parathyroid excess. "I do not diagnose them with osteoporosis--I just recommend further testing for thyroid/parathyroid abnormality."
BY DAMIAN McNAMARA
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|Title Annotation:||Clinical Rounds|
|Publication:||Internal Medicine News|
|Date:||May 1, 2004|
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