Quantitative Influenza Antibody (Nasal or Throat Swab)
Does this test have other names?
Direct immunofluorescence (DFA), indirect immunofluorescence (IFA) antibody staining.
What is this test?
This test checks for influenza antibodies in a sample of secretions from your nose
Influenza is a common illness of the respiratory system. It can have serious health
effects or even be fatal, especially if you have a weakened immune system.
Influenza A is more common and can be more serious. It spreads easily through water
droplets in the air, and often affects many people at the same time during fall and
Healthcare providers can test for influenza, or the "flu," in several ways. One method
uses nasal washes and throat swabs to look for influenza antigens. Results are usually
known quickly, in less than 30 minutes. The method described in this test is immunofluorescence.
It uses a staining technique to look for influenza antibodies. Results may be available
in 1 to 4 hours. Results from these rapid testing methods are not as accurate as conventional
viral cultures—another type of influenza test—but are commonly used as initial screening
tests. Viral cultures may take from three to10 days to yield results.
Why do I need this test?
You may need this test if your healthcare provider suspects that you have the flu.
Symptoms of the flu include:
Symptoms of the flu often appear suddenly, about 1 to 2 days after you are infected.
Your body often fights off an influenza infection within a few days, but some people
develop severe pneumonia or other serious complications.
Even if you do not have immediate signs of infection, you should be tested during
flu season or an influenza outbreak if you:
What other tests might I have along with this test?
Your healthcare provider may also order other tests, including a viral culture, rapid
antigen tests, or reverse transcriptase polymerase chain reaction test.
Testing for influenza antibodies is considered a screening test. Your healthcare provider
may use more accurate tests if he or she thinks that the diagnosis needs to be confirmed.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Normal results are negative, meaning that no influenza antibodies were found and you
likely don't have the flu.
A positive result means that you do have influenza antibodies. A positive result is
more likely to be considered a true positive if other cases of influenza have been
reported in your area at the time you're tested. It's possible to get a false-positive
result, meaning that you are not really infected. Your healthcare provider may do
more tests if needed.
How is this test done?
This test requires a sample of mucus or other respiratory secretions. Your healthcare
provider will use a sterile swab to collect a sample from inside your nose or throat.
Another method of doing this test requires a nasopharyngeal aspirate, or NPA. In this
procedure, your healthcare provider will inject saline solution and collect a sample
through your nose.
Does this test pose any risks?
This test does not pose any serious risks. You may feel discomfort or gagging sensations
when your throat or nasal cavity is swabbed. Collecting an NPA may also be uncomfortable.
What might affect my test results?
Other respiratory infections may cause a false-positive result. Influenza screening
tests are sometimes inaccurate, so a negative test result should be interpreted with
How do I get ready for this test?
You don't need to prepare for this test.