Friday, September 29, 2023

How Do They Do A Flu Test

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Questions For Your Doctor After At

Testing for influenza

If youve recently taken an at-home flu test, the following questions may be useful to discuss with your doctor:

  • How do you interpret my test result?
  • Do you think the at-home test that I took was accurate?
  • Should I have any follow-up testing?
  • Are any treatments or other measures appropriate given my symptoms and test result?

The Accuracy Of Flu Tests Varies Depending On The Type Of Test

  • RIDTs may be quick, but theyre not as accurate as other tests. Theyre able to detect flu viruses between 50% and 70% of the time. If paired with a special reader device, they become slightly more accurate .

  • Rapid molecular assays are much more accurate than RIDTs. Theyre typically between 90% and 95% accurate.

  • RT-PCR tests are also very accurate flu tests. Some studies have even found them to be 98% accurate at detecting flu viruses.

  • According to the Centers for Disease Control and Prevention , immunofluorescence tests have moderate accuracy, but an exact percentage isnt provided. All we can say from this information is that this flu test is less accurate than rapid molecular assays and RT-PCR tests.

No matter which flu test you take, if you get a positive test result, there is a good chance that you are infected with the virus identified by the test. However, it does not rule out the possibility of a coinfection, which means that you may also be infected with another virus or bacteria not included in the test.

If you get a negative result, it means that the genetic material of the viruses being tested were not found in your sample. But as we discussed, it is possible to get a false negative result especially if you have symptoms, exposure risk, or other factors that suggest that you are infected. Your provider may use all of this information in determining the best course of action.

How Long Does A Flu Test Take

Getting a flu test isnt usually a time-consuming experience. Your healthcare professional may use one of several approaches to collect a specimen. These include:

  • Deep nasal swab. This testing method involves inserting a swab about one inch into the nostril. It doesnt require inserting as deeply as a nasopharyngeal swab .
  • Nasopharyngeal or nasal aspirate. A less commonly used method, this involves using a special suction catcher to suction mucus for sample collection. When the suction catheter is very far in the back of the throat, doctors call this nasopharyngeal aspirate.
  • Nasopharyngeal swab. For this test, youll be asked to tilt your head back, and a healthcare provider will swab both nostrils. The swab should be inserted to where theres an equal distance between the nostril and the outer ear opening.
  • Throat or nasal swab. This testing method involves using both a nasal swab as well as a throat swab that reaches back into the tonsil area of the throat.

Each of these testing methods usually takes no more than 1 minute to perform. Its waiting for your results that can prove longer.

Centers for Disease Control and Prevention , rapid flu tests are more accurate in detecting the flu in children compared with adults.

With these and other flu tests, its still possible to get a false negative. A doctor should take your symptoms into account as well as if youve been around anyone who was recently diagnosed with the flu.

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What Does The Test Measure

There are different types of measurements that can be used in at-home tests to detect an influenza virus infection.

Some at-home flu tests measure whether there are any detectable proteins on the surface of the influenza virus called antigens. These viral antigens, when present in the respiratory tract, can then trigger a response from the immune system resulting in the flu-like symptoms. The presence of antigens on a nasal swab or saliva sample can be an indication of an influenza infection.

Another type of at-home flu test measures whether there are any pieces of the viruss genetic material in your test sample and are known as molecular tests. One common type of molecular test uses technology known as reverse transcription polymerase chain reaction .

Testing Presents Challenges For Monitoring Co

How do they test for the corona virus in sweden? See me do the test ...

“The problem is always that it’s actually somewhat difficult to determine if it’s a true co-infection,” Klein said.

For one thing, some people may test positive for COVID-19 on PCR tests long after they actually have the infection sometimes for weeks or months. So someone who tests positive for COVID-19 and the flu might have actually already recovered from COVID-19 and just have the flu, Sifri said. “It’s something that we may end up seeing and having a challenging time sorting out.”

That scenario is most likely to happen if you get tested at a hospital, where PCR samples are routinely tested for multiple viral illnesses at once. Outside of a hospital, those types of panels are rare because they tend to be more expensive, Klein said.

In other medical settings, there may not be the capacity for that type of testing and, therefore, it may be harder to pick up co-infections. Doing a rapid antigen test, for instance, requires you to test for one virus at a time. So if you present with flu-like symptoms and test positive for COVID-19, your doctor may not necessarily decide to test you for something else on top of that.

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How The Flu Is Diagnosed

Michael Menna, DO, is board-certified in emergency medicine. He is an attending emergency medicine physician at White Plains Hospital in White Plains, New York and also works at an urgent care center and a telemedicine company that provides care to patients across the country.

Symptoms of the flu are largely similar to those of the common cold or a respiratory infection, so you may not be able to discern between the issues on your own. Luckily, your healthcare provider can formally diagnose you with the flu with a test that confirms the presence of the influenza virus. However, while fast and non-invasive, a flu test may not always deliver accurate results.

In some cases, your healthcare provider may diagnose you with the flu based on your symptoms, whether or not someone else in your household has the flu, or if cases of influenza are increasing in your area.

Prompt diagnosis of the flu is important, as the infection can have complications, especially for certain individuals. Treatments are available to reduce the duration and intensity of the illness.

When Should I Call My Healthcare Provider About My Flu Test

If you have any questions about your flu test, reach out to your provider. It may be helpful to ask the following questions:

  • How do you interpret my test result?
  • Do you think my test result is accurate?
  • Should I have any follow-up testing?
  • Given my symptoms and result, are there any treatment options or medications you recommend?

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What Is The Flu

Influenza is an acute respiratory illness caused by influenza A or B viruses that routinely spreads through the U.S. during the winter months. Frequent symptoms include fever, headache, fatigue, muscle aches, sore throat, cough, congestion, chills, and a runny or stuffy nose. While this respiratory infection can be mild for many, it is serious and even life-threatening for some. Those most at risk for severe complications are young children, older adults, pregnant women, those with chronic health conditions, or those with weakened immune systems. Many people diagnose themselves with the flu and manage the illness at home with over-the-counter pain relievers. However, getting a flu test and a prescription antiviral medication can reduce the severity and length of your symptoms.

Is There A Test That Can Detect Both Flu And Covid

Flu test can produce false negatives

Yes. There is a test that will check for seasonal flu type A and B viruses and SARS-CoV-2, the virus that causes COVID-19. This test is being used by U.S. public health laboratories for surveillance purposes. Testing for these viruses at the same time will give public health officials important information about how flu and COVID-19 are spreading and what prevention steps should be taken. The test will also help public health laboratories save time and testing materials, and to possibly return test results faster.

The Food and Drug Administration has given CDC an Emergency Use Authorizationexternal icon for this new test. Initial test kits were sent to public health laboratories in early August 2020. CDC will continue to manufacture and distribute these kits.

More information for laboratories is available.

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Knowing When To Test For Flu

  • 1Recognize the symptoms of the flu virus. The flu is a respiratory infection that mostly affects your nose, throat, and lungs. It usually comes on quickly and is also known for causing widespread body aches and pains. Despite popular misconceptions, the flu doesnt actually cause nausea or vomiting . Here are the common symptoms of flu to watch for:XTrustworthy SourceMayo ClinicEducational website from one of the world’s leading hospitalsGo to source
  • Fever over 100.4 °F
  • Sore throat
  • Chills and sweats
  • Dry, persistent cough
  • 2Get a flu test as soon as you experience symptoms for accurate results. A flu test is most accurate within the first 48 hours of when you experience symptoms. If you believe you may have the flu, call your doctor immediately or visit an urgent care center. They can discuss your symptoms with you and decide if you need a flu test.XTrustworthy SourceCenters for Disease Control and PreventionMain public health institute for the US, run by the Dept. of Health and Human ServicesGo to source
  • You dont need to get tested for the flu to receive a diagnosis.
  • If you’ve had a flu shot within the past 7 days, you may get a false positive result on your flu test. This is more common if you received the nasal vaccine. However, you can still get the flu even if you had a flu shot, so don’t dismiss your symptoms.XTrustworthy SourceCenters for Disease Control and PreventionMain public health institute for the US, run by the Dept. of Health and Human ServicesGo to source
  • How Do I Know If I Need To Get A Flu Test

    If you experience any of the following flu symptoms, it might be a good idea to get a flu test:

    • Fever or feeling like you have a fever

    • Chills

    • A runny or stuffy nose

    • Muscle pain

    • Feeling tired

    • Vomiting or diarrhea more common in kids than adults

    Its important to know that everyones flu symptoms are different. You may have some or all of these. But typically, flu symptoms come on quickly .

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    Who Is Considered High Risk

    • Children younger than 5 years old and those older than 65
    • Children or adolescents diagnosed with:
    • Certain respiratory diseases such as asthma
    • Neurological and neurodevelopmental conditions such as seizure disorders
    • Heart disease
  • People younger than 19 years of age who are receiving long-term aspirin therapy
  • People with extreme obesity
  • Children with household members who have compromised immune systems, such as family members with cancer who are receiving chemotherapy
  • Finding A Flu Test Near You


    Rapid influenza tests are available at most urgent care or walk-in clinics as well as your primary care providers office. If youre experiencing flu symptoms, call ahead and ask whether flu tests are offered at that location. Your primary care office should be your first call. Describe your symptoms and ask if they can see you that day.

    Insurance may cover the cost of the test. If you dont have insurance, your healthcare provider may charge anywhere from $50 to $100 in addition to the cost of the office visit.

    Remember, the best way to prevent seasonal influenza is to get a yearly flu vaccine. While the flu shot cant guarantee that you wont get sick, it dramatically reduces your chances, according to the Centers for Disease Control and Prevention . If you do get the flu after having the vaccine, youll likely have a milder course and are less likely to experience serious problems.

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    How Accurate Is A Rapid Flu Test

    A rapid antigen flu test is the least accurate type of flu test. They have moderate sensitivity and high specificity.

    Sensitivity refers to a test’s ability to determine that you have a disease or illness youre positive for the illness. The specificity of a test is its ability to determine that you dont have a disease or illness youre negative for the illness.

    A highly sensitive test means that there are few false-negative results, meaning fewer cases of illness are missed. Since a rapid flu test has moderate sensitivity, its more likely that itll have a false-negative result and miss positive cases. High specificity means that false-positive results are rare.

    Comparison Of Rapid Test And Rt

    In total, 71 of the 200 samples were positive for influenza virus by cell culture: 16 for influenza virus A and 55 for influenza virus B. Two specimens were positive for respiratory syncytial virus and one specimen each was positive for adenovirus, parainfluenza virus type 2, parainfluenza virus type 3, and herpes simplex virus type 1. One culture was contaminated, and 122 samples were negative. One sample showed a cytopathic effect on MDCK cells, but the presence of influenza virus could not be confirmed by immunofluorescence. Since the sample was positive for influenza virus B by Directigen and RT-PCR and positive by QuickVue, the culture was considered positive for influenza virus B.

    Directigen detected influenza virus A in 13 samples confirmed to be positive by viral culture and influenza virus B in 44 samples confirmed to be positive by viral culture but did not detect virus in 9 specimens positive by culture . It gave indeterminate results for 16 samples , of which 1 was positive for influenza virus A, 4 were positive for influenza virus B, 1 was positive for parainfluenza virus type 2, and 1 was positive for parainfluenza virus type 3 by viral culture. Among the samples negative by viral culture, 7 samples were positive by Directigen . Finally, all specimens positive for other respiratory viruses by viral culture were negative by Directigen.

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    Is There Anything Else I Need To Know About A Flu Test

    A new flu vaccine is made each fall. The Centers for Disease Control and Prevention recommends the vaccine for most people 6 months or older. 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.

    Which Is The Best Influenza Swab

    Testing for the flu | Infectious diseases | Health & Medicine | Khan Academy

    Clinicians have several options in swabs when it comes to performing a flu swab test, but not every swab will generate the same level of accuracy. For maximum specimen access, swabs should be transported using appropriate transport media.

    Swab options for flu testing include flocked swabs, cotton tipped swabs, rayon tipped swabs, and foam tipped swabs.

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    What Are The Pros And Cons Of Rapid Influenza Diagnostic Tests

    Advantages of the test

    • RIDTs produce quick results in less than 15 minutes and are simple to perform.
    • Some RIDTs are cleared for office/bedside use.

    Disadvantages of the test

    • Sub-optimal test sensitivity and false-negative results are common, especially when influenza activity is high.
    • Sensitivity of RIDTs used to detect influenza B viral antigens is lower than those used to detect influenza A viral antigens.
    • Although specificity is high, false-positive results can also occur, especially during times when influenza activity is low.
    • Some RIDTs distinguish between influenza A and B viruses, while others do not.
    • RIDTs that provide results on the type of influenza virus do not provide information on influenza A virus subtype or specific virus strain. RIDTs cannot distinguish between seasonal influenza A virus infection and novel influenza A virus infection .

    Polymerase Chain Reaction And Viral Culture Testing

    Laboratories in Massachusetts report all positive influenza laboratory tests to the Massachusetts Department of Public Health , including viral culture and PCR.

    Testing at the State Public Health Laboratory: As part of a more comprehensive respiratory surveillance initiative, MA SPHL performs testing to confirm typing and subtyping of circulating influenza viruses, followed by testing of influenza and SARS-CoV-2 negative samples for the evidence of adenovirus, respiratory syncytial virus A/B, parainfluenza virus types 1-4 , coronavirus HKU1, OC43, NL63, 229E, human metapneumovirus , and rhinovirus/enterovirus , using a multiplex PCR respiratory viral panel.

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    Can The Flu Be Prevented

    While flu testing is available, by the time you have made it to the doctors office, your symptoms are likely pretty miserable. However, it is often possible to prevent or minimize your chances of contracting the flu by getting a flu vaccine and practicing basic hygiene.

    The flu vaccine is developed every year based on information about which strains of the flu are the most likely to be circulating during the coming season. The flu vaccine varies in effectiveness from year to year, with prevention rates typically hovering around 40 to 60 percent.

    Even if the vaccine does not stop you from getting the flu, it may be able to minimize your symptoms and lower your risk of experiencing any complications in the event that you do get infected. As a result, doctors recommend that everyone get their flu vaccine each year.

    Another important defense against the flu is basic hygiene practices like regular handwashing, particularly after touching common surfaces such as a doorknob, kitchen counter, or credit card reader. Washing your hands with warm soap and water for 20 seconds is highly effective at removing the flu virus from your hands if you happen to have picked it up from a nearby surface.

    Additionally, its important to minimize the time you spend around people who appear to be ill, and avoid eating or drinking using the same dishes and utensils as other people.

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