Bone density testing: Who needs it and when

Tiya Dely, a 62-year-old grandmother, feels a sudden, sharp pain in her midback as she bends to pick up her grandson. She has unwittingly fractured a vertebra in her spine because of the bone-thinning disease osteoporosis. Chances are, however, she doesn’t even know she has the disease because she hasn’t had a bone density test to make her aware of her condition.

So, do all women in their 50s need a bone density test? The answer is no, but a great majority could benefit from knowing how their bones measure up. But by age 65, all women should be tested.

Osteoporosis

Osteoporosis is the abnormal thinning of the bone that often accompanies aging. It may lead to fractures and disability, or even death. It affects men, too, though usually at more advanced ages. According to a recent survey published in the American Journal of Public Health, doctors do a poor job of diagnosing and treating osteoporosis. Up to one-third of all postmenopausal women have osteoporosis, but as few as two percent are diagnosed and treated.

Everyone, beginning as early as possible, should take all possible steps to keep their bones strong. Regular weight-bearing exercises (brisk walking, stair-climbing , and others) are essential. So is a good diet, with emphasis on calcium: low-fat or nonfat dairy products as part of a diet based on fruits, vegetables, and whole grains. Most older women need a calcium supplement to get their intake up to the recommended daily 1,200 to 1,500 milligrams of calcium. As you get older, you may also benefit from supplemental vitamin D, which is essential for bone-building. Many multivitamins contain 400 IU of vitamin D, which is the recommended daily intake for those aged 51 to 70 (those over 70 need 600 to 800 IU). Of course, smokers should quit smoking, and drinkers should keep their intake moderate (at most, two drinks daily for a man, one for a woman).

Fortunately, osteoporosis is a largely preventable disease for which there is painless, noninvasive screening technology. If you haven’t had a bone density test, here’s what you need to know to determine whether you need one.

Who Needs It?

The US National Osteoporosis Foundation recommends bone density testing for:

• All women age 65 and older

• All postmenopausal women younger than 65 who have at least one additional risk factor for osteoporosis other than menopause

• All postmenopausal women who’ve had a bone fracture

• All women who would consider taking hormone replacement therapy (HRT) if they knew their bone density results were low.

• All women who have been taking HRT for a prolonged period

Osteoporosis Risk Factors

• Being female

• Thin or small frame or both

• Advanced age

• Family history of osteoporosis

• Postmenopause, including early or surgically-induced menopause

• Diet low in calcium

• Inactive lifestyle

• Cigarette smoking

• Excessive alcohol use

• Being white or Asian

• Use of certain medications, such as corticosteroids and anticonvulsants

• Eating disorders, such as anorexia and bulimia

If you have more than one risk factor, talk to your doctor whether you need to be screened.

Types Of Scans

The preferred method for determining bone mineral density (BMD) – how dense your bones are in your spine, wrist or hip – has been the central dual energy x-ray absorptiometry (DEXA). It uses low-level x-ray to assess your spine, hip or wrist. This test detects with great accuracy how dense or thin your bone is.

If central DEXA isn’t available, your doctor may use a peripheral DEXA, a smaller device that measures bone mass in your hand, wrist, finger or heel.

In 1998, the US Food and Drug Administration (FDA) approved a new device, called a bone sonometer, that transmits sound waves to pass through it. It’s portable and inexpensive, which makes it potentially accessible to more women. It’s accuracy compared with DEXA, however, is under further study.

In 2000, the FDA also gave marketing clearance for a small, tabletop imaging device called MetriScan, which scans your finger and prints out a report on your bone density.

Another method to measure bone is quantitative computerized tomography (QCT). It’s most commonly used to measure spine.

All of these are good screening tests, though the DEXA of the spine and hip is the gold standard for diagnosis.

Results

The results of your BMD test will be reported as a T-score (see diagram). The World Health Organization established the standard for women based on adult young women whose bone mass is at its peak. It’s pretty simple to interpret the readings. The T-scores are derived from the number of standard deviations from those established by the WHO norms. For every standard deviation – one unit decrease – below the norm, the risk of fracture approximately doubles.

If your DEXA T-score is about -1.0, you have normal bone mass. Between -1 and -2.5, you have osteopenia (low bone mass). A T-score at or below -2.5 indicates osteoporosis.

The lower your T-score, the greater your risk of fracture. How often you need to repeat the test depends on the results. If you’re taking medications for osteopenia or osteoporosis, you may benefit from measurement every two to three years to determine the effectiveness of your treatment.

Boning Up

If you have reason to think you’re at risk of osteoporosis, don’t hesitate to ask your doctor about a bone density test. If your scan shows signs of osteoporosis, there are treatments, including a number of medications, that help fight bone loss. Talk to your doctor about taking preventive measures. This includes adequate calcium, vitamin D and regular exercise. It might include medications such as alendronate (Fosamax), risedronate (Actonel), raloxifene (Evista), calcitonin (Miacalcic) or hormone replacement therapy.

These medications work by slowing bone loss. However, a study published last year in the New England Journal of Medicine reports that a new medicine derived from parathyroid hormone actually builds new bone and reduces the risk of fractures. Parathyroid hormone is produced by the tiny parathyroid glands found in your neck. The medication reduces the risk of fracture by at least one-half.

The drug will be marketed under the brand name Forteo, and may be available soon. Although it has only minor side effects – occasional nausea and headache – there’s one drawback. It must be administered by daily injection. Most people, however, seem to quickly learn to do this for themselves in the same way that people with diabetes master giving themselves daily shots of insulin.

Osteoporosis isn’t an inevitable result of growing older. Once you’ve been tested, you and your doctor can discuss the best way to get and keep your bones strong and healthy.