Rapid Influenza Antigen (Nasal or Throat Swab)
Does this test have other names?
Rapid influenza diagnostic test, RIDT
What is this test?
This test quickly checks for signs of the influenza viruses A and B in a sample of
secretions from your nose or throat.
The flu (influenza) is an illness of the respiratory system. Influenza A is more common
than influenza B. It spreads easily through water droplets in the air from coughs
or sneezes of people who are infected. It often affects many people at the same time
during fall and winter.
Symptoms of the flu often show up suddenly. This is about 1 to 4 days after you are
infected. Most people will get better within a few days to less than 2 weeks. But
those with a weakened immune system may get severe pneumonia or other serious problems.
Your healthcare provider can test for the flu in several ways. The rapid influenza
antigen test usually gives results quickly. Immunofluorescence is another test that
may be used. This test uses a staining technique. Results from these tests are not
as accurate as viral cultures. But these tests are faster and easier and are commonly
used for the first screening.
You don't always need an influenza test for your provider to diagnose the flu. Healthcare
providers may make the diagnosis and begin treatment based on your symptoms and a
Why do I need this test?
You may need this test if you have symptoms of the flu to find out whether you have
it. Symptoms of the flu include:
Even if you don't have symptoms, you may need this test during flu season or an influenza
outbreak if you:
What other tests might I have along with this test?
You may also need other tests. These include an immunofluorescence antibody test,
viral culture, or reverse transcriptase polymerase chain reaction test for influenza
DNA. Testing for influenza antigens is considered a screening test. Your healthcare
provider may use more accurate tests if they think the diagnosis needs to be confirmed.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
A negative result means that no signs of the virus were found and that you may not
have the flu. The results of this test should be interpreted with caution because rapid
influenza antigen tests may have a significant number of false-negative results. This
means that you may have the flu even if your results were negative.
A positive result means that signs of the virus were found and that you may have the
flu, especially if other cases of the flu have been reported in your area at the time
you are tested.
It's possible to get a false-positive result, meaning that you aren't really infected.
You may need more tests to confirm this. Your healthcare provider may also treat you
even if you have a negative test result.
How is this test done?
This test requires a sample of mucus or other secretions from your nose or throat.
Your healthcare provider will use a sterile swab to collect the sample.
Another way of taking a sample requires a nasopharyngeal aspirate (NPA). In this procedure,
a healthcare provider will inject saline solution into your nose and then collect
Does this test pose any risks?
You may feel discomfort or gagging when your throat or nasal cavity is swabbed. Collecting
an NPA may also be uncomfortable.
What might affect my test results?
If you have another respiratory infection, you may get a false-positive result.
How do I get ready for this test?
You don't need to prepare for this test. Be sure your healthcare provider knows about
all medicines, herbs, vitamins, and supplements you are taking. This includes medicines
that don’t need a prescription and any illegal drugs you may use.