Questions & Answers
Seasonal Influenza Testing
What laboratory tests are available to detect influenza?
Diagnostic tests available for detecting influenza virus conducted by laboratories include viral culture, polymerase chain reaction (PCR), rapid antigen testing, and immunofluorescence. There also are commercial rapid diagnostic tests available that can be used by laboratories in outpatient settings to detect influenza viruses within 30 minutes. These rapid tests differ in whether or not they can distinguish between influenza A and B viruses. These tests also vary in the chance that they will miss an influenza infection and sometimes falsely detect an infection. During an influenza outbreak, a positive test is likely to indicate influenza infection.
When should patients be tested for influenza?
Influenza can be difficult to diagnose based on clinical symptoms alone because the symptoms of influenza can be similar to those caused by other infectious agents. A number of tests can help in the diagnosis of influenza, but testing does not need to be done for all patients. During an outbreak of respiratory illness, testing for influenza can help determine if influenza is the cause of the outbreak. Influenza testing can also be helpful for managing individual patients. For example, testing can be useful in guiding antiviral or antibiotic treatment and clinical management of high-risk patients.
For practical purposes this season, CDC recommends that tests should be used to establish that flu is present in a patient population. Once this is established, health-care providers should use their clinical judgment for diagnosing and treating mild cases of respiratory illness. The decision to seek testing needs to be guided by the patient's underlying health, course of illness, and other factors, and should be made by their health-care provider. Use of tests for individual patients should most often be reserved for people at high risk from serious influenza complications, where diagnostic or therapeutic decisions could be life-saving.
- Page last reviewed February 15, 2007
- Page last modified November 4, 2004
- Content Source: Coordinating Center for Infectious Diseases (CCID)
- National Center for Immunization and Respiratory Diseases (NCIRD)
