Sunday, April 3, 2011

Heart disease screens don't change treatment

"It is shocking how little evidence there is," Dr. Patrick O'Malley of the Uniformed Services University in Bethesda, Maryland, who wrote an editorial in the Archives of Internal Medicine, where the new report was published.

Looking at earlier studies, the authors found screening people with such tests didn't seem to change what drugs doctors prescribed, nor the patients' diet and exercise habits or whether they smoked.

These are all factors that could influence a person's risk of heart disease, which accounts for more than one out of every three deaths in the U.S., according to the American Heart Association.

The hope is that taking a piercing look at the heart will spot problems like calcium buildups that might one day block its blood supply. In principle, that would allow patients and their doctors to take steps to avert heart attacks, strokes and similar conditions down the road.

CT scans may cost anywhere between a few hundred dollars to a couple of thousand, and expose patients to radiation. But like other tests for heart disease, they have never been proven to improve health in patients without symptoms.

Still, the number of Americans who get these tests has been climbing fast in recent years. Every year, for instance, hundreds of thousands of people get CT scans, an imaging technique based high-dose x-rays. No one knows how many of those are done to look for heart problems in patients who don't have any symptoms.

O'Malley said the tests shouldn't be used on people without chest pain and other symptoms of heart disease outside of clinical experiments.

The report is based on a review of seven earlier studies -- all the authors could find -- that tested whether heart imaging had an impact on people's lifestyle and the treatment they got.

The original studies included a broad swath of people without symptoms of heart disease -- some had major risk factors like diabetes and some were healthy middle-aged people.

Across the board, Dr. Daniel Hackam of the University of Western Ontario in London, Canada, and colleagues found no differences between those who had their heart tested and those who didn't.

But they add the studies were so small -- most included only a few hundred individuals -- that a possible impact couldn't be entirely ruled out.

Along with CT, or computed tomography, researchers also looked at screening with echocardiography, ultrasound, and so-called myocardial perfusion imaging.

None of those tests are recommended for screening purposes by the U.S. Preventive Services Task Force, a federal task force. On the other hand, several medical societies, including the American Heart Association, support their use.

Dr. Allen Taylor, a cardiologist at Georgetown University in Washington, D.C., who wasn't involved in the new work, said the findings didn't mean the tests are no good.

"All you can conclude from that paper is we need some better evidence," he told Reuters Health. "Innovation will stop if there is an irrational demand for evidence beyond refute."

"It's completely about the way information is identified by clinicians and put into practice," he added. "The guidelines are not as clear and that's a gap."

Taylor, who said he has no ties to manufacturers of imaging equipment, explained the tests give a better idea of a patient's risk than traditional risk factors like blood pressure and obesity.

But other experts disagree about their usefulness.

"You get more false information than you get real information," Dr. Rita F. Redberg, a cardiologist at the University of California, San Francisco, told Reuters Health last year.


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