 Confirmed diagnosis of pandemic H1N1 flu requires testing of a nasopharyngeal , nasal or oropharyngeal tissue swab from the patient . Real @-@ time RT @-@ PCR is the recommended test as others are unable to differentiate between pandemic H1N1 and regular seasonal flu . However , most people with flu symptoms do not need a test for pandemic H1N1 flu specifically , because the test results usually do not affect the recommended course of treatment . The U.S. CDC recommend testing only for people who are hospitalized with suspected flu , pregnant women and people with weakened immune systems . For the mere diagnosis of influenza and not pandemic H1N1 flu specifically , more widely available tests include rapid influenza diagnostic tests ( RIDT ) , which yield results in about 30 minutes , and direct and indirect immunofluorescence assays ( DFA and IFA ) , which take 2 – 4 hours . Due to the high rate of RIDT false negatives , the CDC advises that patients with illnesses compatible with novel influenza A ( H1N1 ) virus infection but with negative RIDT results should be treated empirically based on the level of clinical suspicion , underlying medical conditions , severity of illness and risk for complications , and if a more definitive determination of infection with influenza virus is required , testing with rRT @-@ PCR or virus isolation should be performed . Rhonda Medows of the Georgia Department of Community Health states that the rapid tests are incorrect anywhere from 30 % to 90 % of the time and warns doctors in her state not to use them because they are wrong so often . The use of RIDTs has also been questioned by researcher Paul Schreckenberger of the Loyola University Health System , who suggests that rapid tests may actually pose a dangerous public health risk . Nikki Shindo of the WHO has expressed regret at reports of treatment being delayed by waiting for H1N1 test results and suggests , " [ D ] octors should not wait for the laboratory confirmation but make diagnosis based on clinical and epidemiological backgrounds and start treatment early " . 
