Routine but costly stress tests of people who do not have symptoms of coronary artery disease may not always be justified.

But if individuals have certain risk factors, then the stress test can be a valuable and cost-efficient tool, says Dr. Howard S. Weintraub, associate director of stress testing at New York University Medical Center.A stress test, also known as "exercise electrocardiography," measures the heart's response to the physical stress of running on a treadmill in an effort to detect narrowing or obstruction of the coronary arteries.

There are also bicycle and upper-body exercise testing devices that are used for specific diagnostic exams, or when treadmill testing is not feasible. Less frequently, stress testing is used to pinpoint suspected abnormalities in heart rhythm or to evaluate the progress of a cardiac fitness program.

The controversy over stress testing is not related to other devices or uses but only to widespread screening.

Weintraub recommends that people undergo a cardiac stress test only if they are at significant risk for the development of coronary heart disease.

These risk factors include a family history of coronary artery disease before age 55, smoking, a cholesterol level above 240, diabetes and high blood pressure (more than 160/90).

The number of cardiac stress tests being performed has increased dramatically in recent years, with a large proportion of the tests being done on people who do not have symptoms of heart disease.

Many medical experts and consumer health groups question the medical value and cost justification of widespread use of routine stress testing. The high rate of "false positives" leading to unnecessary anxiety and possibly even more expensive testing, has been one of the major criticisms of stress testing.

Weintraub thinks that confining screening stress tests to individuals who have risk factors for heart disease would significantly reduce the number of people who are incorrectly suspected of having coronary blockage.

The duration of exercise is also a critical diagnostic feature. The appearance of an EKG abnormality late in a test can be misinterpreted as a positive or dangerous sign when it may not have any importance. This is one of several factors that would be appreciated by physicians who are experienced in stress testing.

Patients who exercise for the optimal length of time are at a low risk of a heart attack within the next five years, even if they have certain EKG abnormalities.

Weintraub said that stress tests should not be part of a standard check-up. "But if there are symptoms, or significant risk factors, then a stress test may be a useful diagnostic and prognostic tool," he added.