During your next routine medical checkup you have at least a 43 percent chance of undergoing an unnecessary medical test, a new study shows.

It's not like you're getting something for nothing. If you're not having symptoms, and your doctor has no reason to suspect you have a problem, U.S. guidelines advise against giving you a routine urinalysis, electrocardiogram, or X-ray.

"This has more harm than benefit," says Dan Merenstein, MD, director of research in family medicine at Georgetown University. "The problem is, there are so many false-positive results from these tests. They lead to other things, like biopsies.

The tests are meant to help doctors explore specific symptoms that are troubling patients or raise suspicion of a problem. If you're a healthy person who's just getting a routine checkup, there's only a tiny chance the tests will find disease.

But Merenstein points out there's a good chance the tests will get a slightly abnormal finding. That means further costly tests -- maybe even a painful biopsy -- to show that you were, indeed, perfectly healthy to begin with.

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Too Many Tests for Too Many Patients

Merenstein and colleagues analyzed CDC data on more than 4,600 preventive health exams from 1997 to 2002. All these exams were checkups on healthy people, with no specific symptoms that should have triggered special testing.

And yet:

--37 percent of checkups included a urinalysis.

--9 percent of checkups included an electrocardiogram.

--8 percent of checkups included an X-ray.

--43 percent of checkups included at least one of these three tests.

It's an important study, says Robert Schwartz, MD, chairman of the department of family medicine and community health at the University of Miami Miller School of Medicine.

"There are many things we do in primary care that are unnecessary -- unnecessary because there is no proof that by doing these exams we get data that makes a difference to a patient's health care," Schwartz tells WebMD.

Unfortunately, Schwartz says, his experience bears out Merenstein's findings.

"It happens all the time," he says. "The patient has no symptoms and doesn't smoke, but he gets a routine chest X-ray. If there is a small shadow, doctors are obligated to look further. That X-ray becomes a CT scan. That may show a small little nodule. The next thing you know, the patient ends up with a cardiothoracic surgeon who wants a needle biopsy, or even an open biopsy. In a lot of these cases, he comes up with nothing, a benign nodule or something."

Aside from the costs in time and the potential for unnecessary suffering, these procedures add up to big money. Merenstein's modest estimate of the cost of just these three simple tests is $47 million to $194 million a year. And that doesn't include the cost of follow-up tests.

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What to Tell Your Doctor

No doctor, Schwartz says, is ever completely free of worry that he or she might miss something. That, he says, is a major reason for unnecessary tests.

"I can't think of any doctor practicing today where the specter of missing something is not hanging over their heads. This is an underlying theme for everybody in practice," he says. "Unless patients push doctors and say, 'I heard these tests might not be recommended. Why are we doing them?' they may not respond to the message in the Merenstein study."

Doctors often have very good reasons to ask patients to give urine or have an electrocardiogram or X-ray. But don't just assume this is so, says Pedro Cazabon, MD, a general internist at the Ochsner Clinic in New Orleans.

"If you're asked to undergo one of these tests, don't just refuse -- ask your doctor, 'Are you looking for something specific, or is this just screening?' Cazabon tells WebMD. "These tests aren't for screening. But during a routine checkup, people often say something that raises a flag, and that makes you want to do some tests. This is completely different than using these tests to screen in the absence of symptoms."

Merenstein says the doctors, too, have a responsibility to tell patients what they are looking for.

"I don't think anyone should just tell a patient to urinate in a cup," he says. "It should be shared decision making. You should ask the reason for these tests during the visit. Or, if you later wonder why a test was done, you should call back. It should be a give and take. Patients and doctors should be open to talk about what we know and what we don't know. I think you get better medical care that way."

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SOURCES: Merenstein, D. American Journal of Preventive Medicine, June 2006; vol 30: pp 521-527. Dan Merenstein, MD, assistant professor and director of research, department of family medicine, Georgetown University, Washington. Robert Schwartz, MD, professor and chair, department of family medicine and community health, University of Miami Miller School of Medicine. Pedro Cazabon, MD, internal medicine, Ochsner Clinic, New Orleans.