By Genevra Pittman
NEW YORK (Reuters Health) - Some hospitals insert filters into the blood vessels of more than one-third of their patients with clots that may travel to the lungs, despite a lack of evidence they save lives, according to a new study.
The filters, made of metal wires, are recommended based on theories about how they work for patients with a so-called venous thromboembolism who can't take anti-clotting drugs.
But they are sometimes used on other people with blood clots, as well. And the filters may increase the risk of second clots in the legs and other complications - such as when pieces of the filter break off and migrate to the lungs or heart, researchers said.
"The logic is that if we put a little basket, some sort of net, in the inferior vena cava and catch these clots before they get to the lungs, we may be able to save lives," said Dr. Vinay Prasad, from the National Institutes of Health in Bethesda, Maryland.
But, he added, "There is no good evidence that it actually does do that."
Researchers led by Dr. Richard White from the University of California, Davis School of Medicine in Sacramento analyzed discharge records from 263 California hospitals to track use of vena cava filters in 2006 through 2010.
During that time, more than 130,000 people were hospitalized for blood clots. Surgeons across the state inserted a filter into the blood vessels of one in seven patients with clots, but the frequency of filter use varied widely by hospital - from 0 to almost 40 percent of patients.
People having a major operation or with serious bleeding were more likely to get a vena cava filter, but hospital factors seemed to affect their use as well. For example, the largest hospitals used filters five times more than the smallest ones, and urban facilities inserted them more than twice as often as rural ones.
"Everyone in this field of dealing with blood clots has always been concerned about whether these filters do any good or not," White told Reuters Health.
"Everyone's been wondering, why are these things being used so much? You look nationally, and it just keeps going up and up and up."
White said his team is now looking at how well patients did after they did or didn't receive a filter. But he said the researchers were "flabbergasted" at the amount of variation they saw, even from hospitals down the street from one another.
Lack of data on how well the filters work, as well as the type of specialists working at each hospital, likely contributes to some of that variation, he and his colleagues reported Monday in JAMA Internal Medicine.
According to the Centers for Disease Control and Prevention, between 300,000 and 600,000 Americans have a venous thromboembolism ever year and 60,000 to 100,000 die as a result.
Prasad, who wrote a commentary published with the new study, questioned whether filters should be used at all among those patients, given continued questions about the devices' benefits and safety.
"I would advise that in all but the rarest cases, you should not be getting a filter placed," he told Reuters Health. "I'm just not convinced that they work."
The devices cost between $7,000 and $12,000 to insert, Prasad said.
"If your doctor suggests you should get a filter, I think the patient should be asking some really tough questions, such as what is it about their particular situation that they need a filter?" he said.
SOURCE: http://bit.ly/149XYRG JAMA Internal Medicine, online March 18, 2013.