DALLAS -- Tanned, trim and smiling, Marty Baze looked the picture of health as she awaited her first bone density scan for osteoporosis at the Aston Ambulatory Care Center in Dallas.

When it comes to osteoporosis, the retired university teacher, who is "just over 60," knows that looking good on the outside doesn't count.

"I'm Caucasian, northern European and not overweight," she says of the factors that studies have suggested would place her at higher risk of developing the bone-thinning disease.

"Even though I exercise a lot and take calcium supplements and estrogen, I probably should have had this test done earlier," she says.

In fact, medical experts are debating how quickly after menopause women should be tested for osteoporosis. While many doctors are sending their postmenopausal patients for screening tests as early as age 50, other doctors do not even test women after they suffer hip fractures, a classic sign of the disease.

"Historically, these tests have not been very accurate," says Dr. Richard E. Berger, an endocrinologist who runs the Osteoporosis Care Center in North Dallas. "But medically acceptable bone density tests have been available since the mid-'90s, and the awareness of osteoporosis still is lacking."

An estimated 10 million Americans have osteoporosis, 80 percent of them women, and 34 million are believed to have low bone mass, which places them at greater risk of developing the disease, says the National Institutes of Health.

Last month, a national panel of medical experts recommended that most women be screened for osteoporosis starting at age 65. However, certain postmenopausal women -- those ages 60 to 64 who do not take estrogen and who weigh less than 155 pounds -- should also be tested for the disease, notes the U.S. Preventive Services Task Force, which published its recommendations in the Annals of Internal Medicine.

The task force also suggests a two-year interval between screening tests for those women showing signs of rapid bone thinning, which could lead to fractures. But some doctors currently test such women annually. A woman showing little or no signs of bone loss could wait as long as five years between screening tests, suggests a study that accompanied the task force report.

"We're directing our recommendations to patients seen in typical primary-care settings who have no complaints related to osteoporosis," says Dr. Alfred O. Berg, chairman of the task force and professor and chair of family medicine at the University of Washington in Seattle. "It's not uncommon that specialists, who tend to see more complicated patients, would want to screen them" at an earlier age and more often.

Osteoporosis develops as the body removes old bone, a natural process called resorption, and fails to produce enough bone to replace it. Typically, a person's bone mass peaks around age 30 and diminishes slowly until age 80 when, according to the World Health Organization, 70 percent of women suffer from osteoporosis.

Normally, a diagnosis of osteoporosis, or porous bones, comes only after someone breaks a hip or suffers a telltale vertebra fracture. The disease stays "silent" while bone mass progressively thins to the point of fragility, gradually increasing a person's susceptibility to fractures.

Doctors who treat osteoporosis say they are frustrated because they believe new treatments and even lifestyle changes can stop or slow the progression of osteoporosis.

"It's a preventable disease, but it requires looking for it early," Berger stresses. "It's like cholesterol testing -- it gives you an idea where you're heading so you can make changes to slow it down."

To strengthen bone mass as people age, and possibly stave off osteoporosis, doctors recommend diets of calcium-rich foods such as milk products and leafy green vegetables. Doctors also encourage people to take calcium supplements when there are early signs of the disease, and they promote the idea of exercise to build bone mass.

Early testing also might make a dent in the estimated 1.5 million bone fractures, including 300,000 broken hips, related to osteoporosis every year in the United States. Mending those broken bones costs about $17 billion in hospital and nursing-home care, according to the NIH.

It is not known how many women are tested annually for osteoporosis because no scientific survey has been done, says Lynn Chard-Petrinjak, a spokeswoman for the National Osteoporosis Foundation, an advocacy group for disease sufferers. However, one pharmaceutical company has estimated that only 12 percent of the eligible Medicare recipients were tested for osteoporosis last year.

Since 1999, the osteoporosis foundation has recommended testing all women age 65 and over as well as younger postmenopausal women if they have certain risk factors, including being small-boned, having low estrogen levels or having a family history of the disease.

Dr. Khashayar Sakhaee, an osteoporosis expert at the University of Texas Southwestern Medical Center at Dallas, objects to the idea of waiting to screen women until they are 65 and, especially, of allowing women to wait five years between tests if their bone loss is minimal.

"At 3 percent bone loss per year, we leave them five years without a test, losing maybe 15 percent of their bone mass, which doubles their chance of a fracture," he says of the testing frequency mentioned in the new recommendations. "I don't know how they came to this analysis. I think it's cost containment."

The new guidelines did not take into account how much was being spent for osteoporosis testing, says Berg. However, the task force's study notes that Medicare's reimbursement rates for screening range from $34 to $133, depending on the test.

"Most women would require repeated tests over several years before receiving a diagnosis of osteoporosis and leaving the screening pool," the study concluded.

The task force based its screening guidelines on a scientific analysis of previously published studies that looked at the effectiveness of bone-density screening of certain groups of patients, say the authors. They also considered that a new class of drugs for the treatment and prevention of osteoporosis, called biphosphonates, has been on the market for five years. (The drugs also are available for the 1.5 million people who take steroids for more than six months to treat chronic conditions, exposing them to potentially serious bone loss.)

Recent studies have shown that the new class of drugs can restore some bone mass in older women who have suffered at least one fracture due to osteoporosis.

"Our studies look at how to stop this cascading plume of repeat fractures once one fracture has occurred," says Dr. Harry K. Genant, professor of radiology at the University of California, San Francisco.

His most recent study, funded by a partnership of Procter & Gamble Pharmaceuticals and Aventis Pharmaceuticals, found that the drug risedronate, known by the brand name Actonel, caused a 70 percent reduction in moderate and severe vertebral fractures in women who had osteoporosis and one vertebral fracture. They took the drug for a year and were compared with a group of women who took a placebo.