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Flu Test: Detecting Flu Viruses

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In most cases, a doctor can diagnose the flu based on symptoms, especially when these symptoms happen during the peak flu season. But sometimes your doctor may want to do an influenza rapid diagnostic test to be sure the influenza virus is responsible for your symptoms, not another health problem.

Why Is a Flu Test Helpful?

When your doctor distinguishes the flu virus from other viral infections, antiviral drugs can be prescribed early in the illness when they are most effective. If the flu is diagnosed early (within 48 hours of showing flu symptoms), the antiviral drugs may alleviate the severity of the flu symptoms and shorten the illness by a day or so. After 48 hours, these drugs may not have any benefit in reducing flu symptoms.

In addition, a flu test may help reduce the incidence of antibiotics being inappropriately used for the flu virus.


How Does a Flu Test Work?

First, your doctor will take a sample from the back of your nose or throat. To collect this sample, the doctor will swab your nasal passage or throat. The doctor will then seal the sample in a packet and run a rapid test on site or send it to a lab for testing.

How Long Does It Take to Get Flu Test Results?

The rapid diagnostic flu tests usually provide results within 15 minutes.

What Does the Flu Test Detect?

Some rapid flu tests can help distinguish between influenza A and B virus. As with any tests, the accuracy of the test depends on the quality of the manufacturer’s test, sample collection method, and how much viral sample a person is shedding at the time of testing.

WebMD Medical Reference

Reviewed by Jennifer Robinson, MD on January 20, 2015
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