BODY WATCH : Just How Dense Are Your Bones?
Bone-density tests, a kind of “instant snapshot” of your bone status, were not widely available until recently. But in the past five years, the tests have become commonplace.
They can help physicians predict a patient’s risk of developing osteoporosis or forecast the risk of future fractures in people who already have the disease.
Even when the test is not medically necessary, growing numbers of consumers are requesting it. “People want to know where they stand,” says Dr. Joseph Lane, chairman and professor of orthopedic surgery at UCLA.
Here’s what consumers need to know.
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The Candidates: The test can potentially benefit a variety of people. Anyone taking steroid medications for disorders such as asthma, lupus or Crohn’s disease might consider the test because these medicines can affect bone density.
Women experiencing menopause (when bone mass declines) might get a test to help them decide whether to start long-term therapy with estrogen, which can help maintain bone mass.
Anyone who suffered a recent fracture in which osteoporosis is suspected should consider a test, according to the National Osteoporosis Foundation, as should people with multiple risk factors for developing osteoporosis.
That risk factor list is long and includes:
* being female;
* having a small and thin frame;
* having a family history of osteoporosis (more common in women);
* eating a low-calcium diet;
* smoking cigarettes;
* drinking alcohol excessively;
* following a sedentary lifestyle;
* having a history of eating disorders.
A daughter who sees signs of osteoporosis in her mother should also consider the test.
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The Test: A bone-density test detects the amount of bone mass present and evaluates its density, or just how tightly it is packed. Bone can be evaluated at a variety of sites, including the spine, hip, wrist, hand, heel or total body.
Several measurement techniques are available, but the most common one uses a double-beam X-ray.
“The test is painless,” nurse Gina Golde tells patients at the Osteoporosis Medical Center in Beverly Hills as they lie on a padded table to prepare for the 10-minute scan. No undressing is required, but patients are advised to avoid clothing with large metal buttons, buckles or zippers. There are no pretest eating or drinking restrictions.
As a patient lies still, two X-ray beams pass through the body from below. The amount of radiation involved is extremely small, according to manufacturers of the bone-density testing units. A spine scan, for instance, involves less than one-tenth the radiation of a chest X-ray, according to information from Lunar Corp., which manufactures a testing device.
The denser the bone, Golde explains, the less radiation passes through the site being measured and the less radiation is registered on an overhead detector.
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The Results: Information from the radiation detector is fed into a computer and the bone-density measurements are compared to a “reference population,” which takes into account weight, age, sex and ethnic background. These can all affect bone density. Then a person’s bone density is compared to two standards, allowing the physician to tell patients where they stand in relation to someone else of their age and body size, and where they stand compared to young, healthy people with peak bone mass. Normally, bone mass peaks at about age 30.
The newer tests can differentiate areas of arthritis. “A big spur can make you look like you’ve got good bone density,” Lane explains. But the more sensitive tests can now tell the difference.
If bone-density readings are low, it could mean bone was lost or not enough bone was formed earlier in life.
The results have a number of applications, helping a physician decide whether steroid medication doses should be altered, whether estrogen-replacement therapy is wise, and how likely a fracture is in the future.
Using repeat testing, a doctor can evaluate how well estrogen-replacement therapy is working to stem bone loss or how altered medication levels are affecting bone density.
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The Law: Effective January, 1994, California enacted a law requiring insurance reimbursement of bone-density measurement and other services for osteoporosis when deemed medically necessary.
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The Costs: Fees for the tests vary widely. In Southern California, the average is $150 or more per test.
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Caveat: Follow-up tests should be done, if possible, on the same machine and at the same facility to minimize errors and inaccurate comparisons.
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* Doheny cannot answer mail personally but will attempt to respond in this column to questions of general interest. Please do not telephone. Write to Your Body, Life & Style, Times Mirror Square, Los Angeles, Calif. 90053.
