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Flu (Influenza) Test

What is a flu (influenza) test?

Influenza, known as the flu, is a respiratory infection caused by a virus. The flu virus usually spreads from person to person through coughing or sneezing. You can also get the flu by touching a surface that has the flu virus on it, and then touching your own nose or eyes.

The flu is most common during certain times of the year, known as flu season. In the United States, flu season can begin as early as October and end as late as May. During each flu season, millions of Americans get the flu. Most people who get the flu will feel sick with muscle aches, fever, and other uncomfortable symptoms, but will recover within a week or so. For others, the flu can cause very serious illness and even death.

A flu test can help your health care provider figure out if you have the flu, so you can get treated earlier. Early treatment may help lessen the symptoms of the flu. There are a few different types of flu tests. The most common is called the rapid influenza antigen test, or rapid influenza diagnostic test. This type of test can provide results in less than half an hour but is not as accurate as some other types of flu tests. More sensitive tests may require your health care provider to send samples to a specialized lab.

Other names: rapid flu test, influenza antigen test, rapid influenza diagnostic test, RIDT, Flu PCR

What is it used for?

Flu tests are used to help figure out whether you have the flu. Flu tests are also sometimes used to:

  • Figure out whether an outbreak of respiratory illness in a community, such as a school or nursing home, has been caused by the flu.
  • Identify the type of flu virus that is causing infections. There are three main types of flu viruses: A, B, and C. Most seasonal flu outbreaks are caused by the A and/or B flu viruses.
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Why do I need a flu test?

You may or may not need a flu test, depending on your symptoms and risk factors. Symptoms of the flu include:

  • Fever
  • Chills
  • Muscle aches
  • Weakness
  • Headache
  • Stuffy nose
  • Sore throat
  • Cough

Even if you have flu symptoms, you may not need a flu test, because many cases of the flu don’t need special treatment. 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:

  • Have a weakened immune system
  • Are pregnant
  • Are over the age of 65
  • Are under the age of 5
  • Are in the hospital

What happens during a flu test?

There are a couple of different ways to get a sample for testing:

  • Swab test. Your health care provider will use a special swab to take a sample from your nose or throat.
  • Nasal Aspirate. Your health care provider will inject a saline solution into your nose, then remove the sample with gentle suction.

Will I need to do anything to prepare for the test?

You don’t need any special preparations for a flu test.

Are there any risks to the test?

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.

What do the results mean?

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.

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Is there anything else I need to know about a flu test?

Most people recover from the flu within a week or two, whether or not they take flu medicine. So you probably won’t need a flu test, unless you are at risk for flu complications.

References

  1. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Influenza (Flu): Children, the Flu; and the Flu Vaccine [updated 2017 Oct 5; cited 2017 Oct 11]; [about 4 screens]. Available from: https://www.cdc.gov/flu/protect/children.htm
  2. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Influenza (Flu): Diagnosing Flu [updated 2017 Oct 3; cited 2017 Oct 11]; [about 4 screens]. Available from: https://www.cdc.gov/flu/about/qa/testing.htm
  3. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Influenza (Flu): Disease Burden of Influenza [updated 2017 May 16; cited 2017 Oct 11]; [about 3 screens]. Available from: https://www.cdc.gov/flu/about/disease/burden.htm
  4. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Influenza (Flu): Flu Symptoms and Complications [updated 2017 Jul 28; cited 2017 Oct 11]; [about 4 screens]. Available from: https://www.cdc.gov/flu/consumer/symptoms.htm
  5. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Influenza (Flu): Flu Symptoms & Diagnosis [updated 2017 Jul 28; cited 2017 Oct 11]; [about 3 screens]. Available from: https://www.cdc.gov/flu/symptoms/index.html
  6. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Influenza (Flu): Rapid Diagnostic Testing for Influenza: Information for Health Care Professionals [updated 2016 Oct 25; cited 2017 Oct 11]; [about 4 screens]. Available from: https://www.cdc.gov/flu/professionals/diagnosis/rapidclin.htm
  7. Johns Hopkins Medicine [Internet]. The Johns Hopkins University; Health Library: Influenza (Flu) [cited 2017 Oct 11]; [about 3 screens]. Available from: http://www.hopkinsmedicine.org/healthlibrary/conditions/adult/respiratory_disorders/influenza_flu_85,P00625
  8. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Influenza: Overview [updated 2017 Jan 30; cited 2017 Oct 11]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/conditions/influenza
  9. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Influenza Tests: The Test [updated 2017 Mar 29; cited 2017 Oct 11]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/flu/tab/test
  10. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Influenza Tests: The Test Sample [updated 2017 Mar 29; cited 2017 Oct 11]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/flu/tab/sample
  11. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2017. Influenza (flu): Diagnosis; 2017 Oct 5 [cited 2017 Oct 11]; [about 4 screens]. Available from: http://www.mayoclinic.org/diseases-conditions/flu/diagnosis-treatment/drc-20351725
  12. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2017. Influenza (flu): Overview; 2017 Oct 5 [cited 2017 Oct 11]; [about 3 screens]. Available from: http://www.mayoclinic.org/diseases-conditions/flu/symptoms-causes/syc-20351719
  13. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co Inc.; c2017. Influenza (Flu) [cited 2017 Oct 11]; [about 2 screens]. Available from: https://www.merckmanuals.com/home/infections/respiratory-viruses/influenza-flu
  14. National Institute of Allergy and Infectious Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Influenza Diagnosis [updated 2017 Apr 10; cited 2017 Oct 11]; [about 5 screens]. Available from: https://www.niaid.nih.gov/diseases-conditions/influenza-diagnosis
  15. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Influenza (Flu) [cited 2017 Oct 11]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=85&contentid;=P00625
  16. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Rapid Influenza Antigen (Nasal or Throat Swab) [cited 2017 Oct 11]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=rapid_influenza_antigen
  17. World Health Organization [Internet]. World Health Organization; c2017. WHO recommendations on the use of rapid testing for influenza diagnosis; 2005 July [cited 2017 Oct 11]; [about 3 screens]. Available from: http://www.who.int/influenza/resources/documents/RapidTestInfluenza_WebVersion.pdf?ua=1
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