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    How CDC Classifies Flu Severity each Season in the United States Information for Laboratories Understanding Influenza Viruses WHO Collaborating Center for Surveillance, Epidemiology and Control of Influenza Viral Genomic Sequencing Infrastructure View All
August 12, 2024
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  Influenza Virus Testing Methods
          Purpose
          Table depicting Influenza virus testing methods.
        Table: Influenza Virus Testing Methods
                Table 1: Influenza Virus Testing Methods
                  Method1                                                                                                                                       Types Detected  Acceptable Specimens2                                                                                          Test Time                                   CLIA Waived3
                  Rapid Influenza Diagnostic Tests (antigen detection)4                                                                                         A and B         NP swab, aspirate or wash, nasal swab, aspirate or wash, throat swab                                           <15 min.                                    Yes/No      
                  Rapid Molecular Assay [influenza viral RNA or nucleic acid detection]                                                                         A and B         NP swab, nasal swab                                                                                            15-30 minutes5                              Yes/No5     
                  Immunofluorescence, Direct (DFA) or Indirect (IFA) Florescent Antibody Staining [antigen detection]                                           A and B         NP swab or wash, bronchial wash, nasal or endotracheal aspirate                                                1-4 hours                                   No          
                  RT-PCR6 (singleplex and multiplex; real-time and other RNA-based) and other molecular assays [influenza viral RNA or nucleic acid detection]  A and B         NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum                             Varies (1 to 8 hours, varies by the assay)  No          
                  Rapid cell culture (shell vials; cell mixtures; yields live virus)                                                                            A and B         NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum; (specimens placed in VTM)  1-3 days                                    No          
                  Viral tissue cell culture (conventional; yields live virus)                                                                                   A and B         NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum (specimens placed in VTM8)  3-10 days                                   No          
          Abbreviations
          FDA = U.S. Food and Drug Administration
          A = aspirate
          B = bronchial
          BAL = broncheoalveolar lavage
          N = nasal
          NP = nasopharyngeal
          S = swab
          T = throat
          TR = tracheal
          UTM = universal transport media
          VTM = viral transport media
          W = wash
    August 12, 2024
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          National Center for Immunization and Respiratory Diseases (NCIRD)
          References
           1. Serologic (antibody detection) testing is not recommended for routine patient diagnosis and cannot inform clinical management. A single acute serum specimen for seasonal influenza serology is uninterpretable and should not be collected. Serological testing for detection of antibodies to seasonal influenza viruses is useful for research studies and requires collection of appropriately timed acute and convalescent serum specimens and testing of paired sera at specialized research or public health laboratories.
           2. Approved clinical specimens vary by influenza test. Consult the manufacturer's package insert for the approved clinical specimens for each test. Ref: Leland, et al. 2007, Clin Micro Rev 20: 49-78. Approved respiratory specimens vary among FDA cleared influenza assays.
           3. Clinical Laboratory Improvement Amendments (CLIA) of 1988. http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/index.html
           4. Chromatographic- and/or fluorescence-based lateral flow and membrane-based immunoassays. Some approved rapid influenza diagnostic assays utilize an analyzer reader device.
           5. Rapid molecular assays can provide results in approximately 15-30 minutes.
           6. Reverse transcription polymerase chain reaction, including FDA-approved test systems, laboratory testing using analyte specific reagents, or lab-developed reagents. Some approved molecular assays can produce results in approximately 60-80 minutes.
          Sources
            * Conjunctival swabs are currently approved under FDA enforcement discretion for testing with the CDC Influenza A/H5 subtyping assay.
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