- The flu has reached your community,
- You have clinical symptoms that are essentially the same as the symptoms of other patients with known cases of the flu,
- You have no evidence of secondary complications,
then your doctor may diagnose you as having the flu without actually testing for influenza. If you are outside the 48-hour window of anti-viral treatment, they may just send you home to rest, drink fluids, and use over the counter remedies to soothe your symptoms. (This is what doctors did before flu testing and treatment were available.)
So why order the flu test at all? Because the flu can be deadly, because knowing it is in the community can help your doctor minimize its spread and because there is treatment available that can lessen its severity if it is diagnosed early. (Of course the best treatment is prevention - getting a flu shot.) The flu test is used to help diagnose influenza A and B, and to differentiate them from other viral and bacterial infections which may be serious and must be treated differently.Rapid (same day) flu tests are best used within the first 48 hours of symptoms to help diagnose influenza and determine whether or not anti-viral medications should be used, or they are ordered within the first week to help identify outbreaks. Viral cultures are usually used to track flu outbreaks and to identify the particular strain that is causing them (sometimes the influenza will mutate enough to make the flu vaccine less effective and sometimes an unexpected flu strain will predominate). Viral cultures are also be used to identify other viral infections that cause clinical symptoms similar to the flu. Currently, the rapid influenza antigen test and the fluorescent antibody detection of influenza cannot distinguish seasonal influenza from avian influenza (bird flu). Influenza virus grown in culture could be sent to a public health laboratory to determine if the strain of influenza A is the antigenic type (H5N1) found in birds and chickens.