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Is it the flu? Get the fast flu test

By Manav Tanneeru
CNN
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(CNN) -- Fast flu tests, which drastically cut the time to diagnose a patient with influenza or not, are helping doctors better treat the illness, according to a recent study and medical experts.

Each year, between 5 percent and 20 percent of U.S. residents are infected with the flu, about 36,000 people die of it and more than 200,000 people are hospitalized, according to the U.S. Centers for Disease Control and Prevention in Atlanta, Georgia.

Timing is key in treating the flu, said Dr. Greg Poland of the Mayo Clinic in Rochester, Minnesota.

If diagnosed early enough -- from 24 to 48 hours after a patient first shows symptoms -- a treatment of antiviral drugs can alleviate the severity of symptoms, cut down on the number of days sick and decrease potential complications, Poland said.

"I think all through my career, what the medical system tried to teach people is that when you have a virus or influenza, don't come in because there is nothing we can do," Poland said. "Now, what we are saying is that medical science has advanced."

The rapid diagnostic tests, as the name implies, can take anywhere from five to 30 minutes to come up with a diagnosis. In contrast, results for a traditional viral culture test can take several days to a week.

The rapid tests generally involve a nasal or throat swab and can be examined in the doctor's office. A viral culture also usually collects a fluid sample that is sent to a laboratory.

The use of these rapid tests has been growing during the past few years and more than 10 variations of the tests have been approved by the Food and Drug Administration, the CDC said.

Depending on the test used and if conducted properly, they register about a 70 percent accuracy rate in diagnosing whether a patient has the flu and are about 90 percent specific in figuring out what type of flu it is, the CDC said.

"Done improperly, and I think a lot get done improperly, the sensitivity falls dramatically," Poland said.

The traditional culture tests are more consistently accurate and they can distinguish between flu subtypes with more specificity. "The gold standard is still a culture, but the gold standard is not timely, hence its usefulness in diagnosis and treatment is limited," Poland said.

Research shows the tests are having an effect on treatment.

Rapid testing has led to a decreased use of antibiotics in the treatment of children with the flu, according to a recent study conducted by Rochester General Hospital and the University of Rochester School of Medicine and Dentistry.

The tests also have helped lead to shorter hospital stays for kids and lessened the amount of extra laboratory testing, the study said.

The test and the accompanying antiviral drug treatment also are a boon for adults who cannot afford to get sick or miss work, Poland said.

The diagnostic tests also could be a benefit for the public health sector because they make it easier to keep track of test results.

In some cases, especially with longer laboratory testing periods, different doctors and nurses may handle the testing process and reporting the results to public health agencies gets lost in the shuffle, Poland said.

However, with a rapid test, where results are in-house and the process is shorter, the reporting is more accurate. Consequently, surveillance of possible outbreaks across the country is enhanced, doctors said.

Context plays an important role in deciding when to use the test, said Dr. Henry Bernstein of the Children's Hospital at Dartmouth in New Hampshire and also a member of the American Academy of Pediatrics' committee on infectious diseases.

For example, early in the season -- the U.S. flu season can last from late December through March -- the rapid tests are useful because many patients mistake symptoms of other illnesses for the flu, he said.

However, in the midst of the flu season when a specific community might be overrun by the illness, the tests might be impractical or a waste of money. Environmental conditions and the prevalence of positive cases would determine whether to perform the tests.

The reasons for being judicious in using the tests -- especially if done improperly, increasing the chances of an inaccurate diagnosis -- are twofold, doctors say. Antiviral doses are limited each flu season and prescribing them indiscriminately could build a resistance to the drugs in the community, doctors say.

The rapid diagnostic tests have been around for several years and are widely used, with some insurance plans covering them. Yet only now are people growing more aware of them, said Poland.

"It's very uneven ... as to whether people understand that those tests are out there and understand that there is treatment for it if they come in soon enough."


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Rapid flu tests can give patients a head start on treatment -- if they truly have influenza.

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