REDI-US Study Influenza Testing

REDI-US Study Influenza Testing

How Did the Influenza Test Work?

When you are sick with influenza, proteins and molecules that are part of the influenza virus can be found in your respiratory tract.  Molecules that can stimulate an immune response are called antigens, and these particles are usually only present for up to five days after someone has been infected with influenza (they are usually found when someone is infectious and shedding influenza virus).

The REDI-US Study used a rapid influenza test, the QuickVue Influenza A+B test.  This test is designed to target the antigens for influenza A and B, and distinguish between them for a more precise diagnosis.  The transient presence of these antigens is why it is important for people to be tested for influenza within a few days of the onset of their symptoms.

While no rapid test made to diagnose influenza is perfect, some are better than others.  Many health professionals and clinics, including the Tang Center, use the QuickVue Influenza A+B test.

What Type of Specimen was Collected for the Test?

During the influenza test, a swab that looks like a long Q-tip is gently swirled around the inside of one of your nostrils.  This swab picks up antigens from influenza A or B that may be found in the nose.  This swab is then transported to a laboratory where the rest of the influenza test is run.

How was the Specimen Tested?

An "extraction reagent solution" is prepared and the nasal swab is swirled in this solution.  The solution "extracts" any influenza A or B molecules that may be part of the nasal swab specimen.  These molecules are left in the solution after the swab is removed.  Next, a test strip is inserted in the solution and the liquid moves up the test strip via capillary action (think elementary school science experiment when water moves up a vertical piece of a paper towel).  This test strip has been made with molecules (antibodies) that react with the influenza A or B antigens if they are present, as well as a general molecule that serves as a control. 

How are Results Interpreted?

After the test is done, a blue control line will always be shown on the test strip. Additional lines appear depending on whether influenza A or influenza B was detected.  No additional lines appear if neither influenza A nor B was detected.

In particular, one pink line indicates that antigens for influenza A were present in their nasal swab, and a diagnosis of Influenza A is made.  A different pink line indicates that antigens for influenza B were present and thus a diagnosis of Influenza B is made.  If neither pink line was seen, that means no antigens for influenza A or B were detected in the nasal swab.  This could be the result if someone was infected with one of many other viruses that cause cold or flu like symptoms, and not influenza A or B itself.  Or, someone may have been infected with influenza A or B but was tested after they stopped shedding influenza A or B antigens in their nose, in which case the test could not pick up any record of their previous illness.