Nasopharyngeal culture test helps to identify disease-causing organisms in nasal secretions. A sterile swab is gently inserted through the nose into the nasopharynx. The cultures help in identifying the types of bacteria which in turn help in determining the suitable antibiotic therapy.

One of the most common tests for flu, RIDT helps in detecting virus in samples of nasal secretions. The test maybe completed in the doctor’s chamber in less than 30 minutes or sent to a laboratory, with results available within a day. This test identifies influenza virus from the other bacteria and viruses with similar symptoms. RIDT is best when done within 48 hours of the onset of symptoms.They diagnose the influenza virus and determine a suitable treatment option. Some rapid tests may be able to only identify influenza A, others may detect both A and B but not differentiate between the two. Still others can both detect and distinguish between influenza A and B but none of the rapid tests can differentiate between the strains of influenza A, for e.g., the H1N1 virus. The main disadvantage of these tests is their inaccuracy, as these tests might miss almost 30% of influenza cases.

DFA is more efficient than the rapid influenza antigen tests but they take several hours to produce a result, require specialized equipments to perform and are not done in a doctor’s office. Samples are usually sent to a laboratory to be tested and interpreted. DFA detects influenza A or B in nasal secretion samples. However, a negative result with this test cannot eliminate the occurrence of influenza entirely. DFA cannot differentiate between seasonal influenza, 2009 H1N1 influenza A or avian influenza.

IFA test helps in influenza A sub-typing. Immuno-fluorescence depends on the quality of the specimen and has an unknown sensitivity in detecting the virus in clinical samples. A negative Immuno-fluorescence might be a false negative and thus the IFA test should not be assumed as a final test for confirming or ruling out influenza A (H1N1) infection.

This quick test for diagnosing H5 strains of avian influenza, commonly bird flu, was approved by the U.S. Food and Drug Administration in the year 2006. The test primarily checks the presence of the Influenza A H5 strain. Once confirmed, further testing is required for determining the exact subtype of the virus. The preliminary test results can be known in less than 4 hours.

Viral Culture is performed to confirm a positive rapid test result. In this test, the virus is actually grown and identified in the laboratory. This test is quite useful for documenting the strains of the virus circulating in the community and for determining the anti-viral agents which would be effective in their treatment. Identifying outbreaks is primarily important in prevention and treatment of widespread flu. Although a very efficient test, viral culture may take up to 3 to 10 days for results.

This molecular testing is the most sensitive diagnostic test for influenza virus. These tests help in detecting influenza A, mostly in critically ill patients and help track an outbreak. However, some false negatives might occur with this test. The test is not widely available yet and results might take up to several days.

These are basically blood tests performed to determine the body’s immune response to the infection. Acute and convalescent samples are tested to confirm flu as the cause of infection. These tests are not routine tests and are generally done for public health or research purposes.

Shell vial culture is a rapid culture method which can detect the presence of a virus within 24 to 48 hours. Shell vial culture has replaced many of the traditional culture methods which usually take several days for detecting the virus. A variation on the standard tissue culture, shell vial culture makes use of a living cell system.