CHICAGO (AP) - An artery disease that is strongly linked to heart attacks and strokes is underdiagnosed and undertreated, despite widespread availability of a simple test, a study says.

The research in Wednesday's Journal of the American Medical Association suggests that peripheral arterial disease or PAD, previously estimated to affect about 8 million to 12 million Americans, may be more common than previously thought.

It also suggests that doctors are overlooking the disease in part because leg pain - considered a classic symptom - may be present in just 10 percent of patients.

Compared with healthy patients, those with PAD face at least four times the risk of developing a heart attack or stroke. But the study indicates primary-care doctors may be underestimating the disease's severity and are not giving patients appropriate treatment that could reduce their risk, the researchers said.

"PAD is equally important to American health as heart disease itself," said Dr. Alan T. Hirsch, a vascular medicine specialist at the University of Minnesota and the study's lead author.

The condition, also known as peripheral vascular disease, is a narrowing of blood vessels and arteries in the legs and sometimes arms. It usually stems from the same type of fatty plaque buildup that causes hardening of the arteries leading to the heart.

The research involved 6,979 high-risk patients - over age 70 or between ages 50 and 69 but with a history of smoking or diabetes. The authors evaluated how well the disease would be diagnosed in 350 primary-care doctors' offices in 25 cities, using a simple test that compares blood pressure in the arms and ankles.

Overall, 1,865, or 29 percent of the nearly 7,000 patients tested, had PAD - 823 whose disease was diagnosed by the physicians during the study and about 1,000 whose diseases had already been diagnosed.

Among those already diagnosed, the study found, only about half of the doctors treating them said they knew of the previous diagnosis - even though the patients' charts contained documentation about it.

Doctors had either forgotten about their own diagnoses or - more likely - were unaware of diagnoses made by others, said co-author Dr. Michael Criqui of the University of California-San Diego School of Medicine. Either way, he said, the results suggest doctors weren't paying attention to a serious condition that should have been suspected because of the patients' risk factors.

Among already-diagnosed patients, more than 40 percent had not been prescribed aspirin or other blood-thinning medications, and 12 percent were not on blood pressure drugs.

Criqui said many doctors think of the disease as a leg problem, even though the study found that only about 10 percent of patients have classic leg pain.

Doctors should be using the ankle-arm blood pressure measurement to routinely screen high-risk patients, Criqui said.

"If you rely on leg pain alone to catch PAD, you miss 90 percent of PAD patients," Criqui said.

Dr. Kenneth Ouriel of Cleveland Clinic Foundation, wrote a JAMA editorial calling the study "an important reminder for primary care clinicians to be cognizant of PAD and its associated signs and symptoms."

Identifying patients earlier will lead to earlier treatment that "can be expected to improve the overall health status and life expectancy of elderly patients with athersclerosis," Ouriel said.

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