More sensitive tests may require your health care provider to send samples to a specialized lab. Flu tests are used to help figure out whether you have the flu. Flu tests are also sometimes used to:. You may or may not need a flu test, depending on your symptoms and risk factors. Symptoms of the flu include:. Even if you have flu symptoms, you may not need a flu test. Most people recover from the flue within a week or two, whether or not they take flu medicine. But your health care provider may order a flu test if you have risk factors for flu complications.
You may be at a higher risk for serious illness from the flu if you:. You may feel a gagging sensation or even a tickle when your throat or nose is swabbed. The nasal aspirate may feel uncomfortable. These effects are temporary. A positive result means you may have the flu. Your health care provider may prescribe medicine to help prevent flu complications. A negative result means you likely don't have the flu, and that some other virus is probably causing your symptoms.
Your health care provider may order more tests before making a diagnosis. If you have questions about your results, talk to your health care provider. Learn more about laboratory tests, reference ranges, and understanding results.
A new flu vaccine is made each fall. It is especially recommended for people in high-risk groups, such as young children, adults over the age of 65, and individuals with pre-existing conditions, such as asthma or heart disease. If you have questions about the flu vaccine, talk to your health care provider. In addition, other viruses can also cause respiratory illness similar to flu. So, it is impossible to tell for sure if you have flu based on symptoms alone.
If your doctor needs to know for sure whether you are sick with flu, there are laboratory tests that can be done. A number of tests are available to detect flu viruses in respiratory specimens. These tests can provide results within approximately minutes but may not be as accurate as other flu tests. Therefore, you could still have flu, even though your rapid test result is negative.
Rapid molecular assays produce results in minutes and are more accurate than RIDTs. In addition to RIDTs and rapid molecular assays, there are several more accurate flu tests available that must be performed in specialized laboratories, such as those found in hospitals or public health laboratories.
These tests include reverse transcription polymerase chain reaction RT-PCR , viral culture, and immunofluorescence assays. All of require that a health care provider swipe the inside of your nose or the back of your throat with a swab and then send the swab for testing. Results may take one to several hours. During a flu outbreak, a positive rapid flu test is likely to indicate flu virus infection. However, rapid tests vary in their ability to detect flu viruses, depending on the type of rapid test used, and on the type of flu viruses circulating.
Also, rapid tests appear to be better at detecting flu in children than in adults. This variation in ability to detect viruses can result in some people who are infected with flu having a negative rapid test result. This situation is called a false negative test result. Despite a negative rapid test result, your health care provider may diagnose you with flu based on your symptoms and their clinical judgment. While your doctor may test you for flu, not everyone who goes to the doctor with flu-like symptoms will be tested.
More information about Antiviral Drugs and recommendations on their use. Testing is not needed for all patients with signs and symptoms of influenza to make antiviral treatment decisions See Figures Once influenza activity has been documented in the community or geographic area, a clinical diagnosis of influenza can be made for outpatients with signs and symptoms consistent with suspected influenza, especially during periods of peak influenza activity in the community.
RIDTs can be useful to identify influenza virus infection as a cause of respiratory outbreaks in any setting, but especially in institutions i.
Positive RIDT results from one or more ill persons with suspected influenza can support decisions to promptly implement infection prevention and control measures for influenza outbreaks.
However, negative RIDT results do not exclude influenza virus infection as a cause of a respiratory outbreak because of the limited sensitivity of these tests. Testing respiratory specimens from several persons with suspected influenza will increase the likelihood of detecting influenza virus infection if influenza virus is the cause of the outbreak, and use of molecular assays such as RT-PCR is recommended if the cause of the outbreak is not determined and influenza is suspected.
Public health authorities should be notified promptly of any suspected institutional outbreak and respiratory specimens should be collected from ill persons whether positive or negative by RIDT and sent to a public health laboratory for more accurate influenza testing by molecular assays and viral culture. Proper interpretation of RIDT results is very important for clinical management of patients and for assessing suspected influenza outbreaks.
A number of factors can influence the results of RIDTs. The accuracy of RIDTs depends largely on the conditions under which they are used. Understanding some basic considerations can minimize being misled by false-positive or false-negative results. Clinicians should contact their local or state health department for information about current influenza activity.
For more information about influenza activity in the United States during the influenza season, visit the Weekly U. Influenza Surveillance Report FluView. Influenza testing is recommended for hospitalized patients with suspected influenza. However, empiric antiviral treatment should be initiated as soon as possible for hospitalized patients with suspected influenza without the need to wait for any influenza testing results see Antiviral Drugs, Information for Health Care Professionals.
Infection prevention and control measures should be implemented immediately upon admission for any hospitalized patient with suspected influenza even if RIDT results are negative see Prevention Strategies for Seasonal Influenza in Heath Care Settings.
Serology for influenza should not be performed for clinical management. Clinicians should understand that negative results of influenza testing do not exclude influenza virus infection, especially if the time from illness onset to collection of respiratory specimens is more than 3 days, or if upper respiratory tract specimens were tested and the patient has lower respiratory tract disease. If influenza is suspected, testing of clinical specimens collected from different respiratory sites can be done e.
Detection of influenza virus infection and prompt implementation of infection prevention and control measures is critical to prevention of nosocomial influenza outbreaks.
When there is influenza activity in the community, clinicians should consider influenza testing, including viral culture, for patients who develop signs and symptoms of influenza while they are in a health care facility. This should be done as part of a broader surveillance strategy for influenza as discussed in Prevention Strategies for Seasonal Influenza in Heath Care Settings.
For suspected influenza outbreaks in institutions, respiratory specimens should be collected from patients with suspected influenza as early as possible once the outbreak is suspected See Figure 2.
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