Rapid influenza diagnostic tests (RIDTs) for influenza can help in the diagnosis and management of patients who present with signs and symptoms compatible with influenza. They also are useful for helping to determine whether outbreaks of respiratory disease, such as in nursing homes and other settings, might be due to influenza. See Guidance for Clinicians on the Use of Rapid Influenza Diagnostic Tests for more information.
Reliability and Interpretation of Rapid Test Results
Proper interpretation of test results is very important for accurate clinical management of patients with suspected influenza. The reliability of rapid diagnostic tests depends largely on the conditions under which they are used. Understanding some basic considerations can minimize being misled by false-negative or false-positive results.
Sensitivities of rapid influenza diagnostic tests are approximately 50-70%, and specificities of rapid diagnostic tests for influenza are approximately 90-95%, when compared with viral culture or reverse transcription polymerase chain reaction (RT-PCR)
Use rapid diagnostic tests with high sensitivity and specificity.
Collect respiratory tract specimens as early in the illness as possible, (within 3-4 days of illness onset).
Follow manufacturer’s instructions, including handling of respiratory specimens, as described in the device package insert.
Consider sending respiratory specimens for RT-PCR to confirm results of rapid influenza diagnostic tests especially when community influenza activity is low and the rapid diagnostic test result is positive or when the rapid diagnostic test result is negative but influenza activity in the community is high. (Contact your local or state health department for information about influenza activity).
NP5 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
NP5 swab, nasal swab
<20 minutes6
Yes/No6
Immunofluorescence, Direct (DFA) or Indirect (IFA) Florescent Antibody Staining [antigen detection]
A and B
NP4 swab or wash, bronchial wash, nasal or endotracheal aspirate
1-4 hours
No
RT-PCR7 (singleplex and multiplex; real-time and other RNA-based) and other molecular assays [influenza viral RNA or nucleic acid detection]
A and B
NP5 swab, throat swab, NP5 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
NP5 swab, throat swab, NP5 or bronchial wash, nasal or endotracheal aspirate, sputum; (specimens placed in VTM8)
1-3 days
No
Viral tissue cell culture (conventional; yields live virus)
A and B
NP5 swab, throat swab, NP5 or bronchial wash, nasal or endotracheal aspirate, sputum (specimens placed in VTM8)
3-10 days
No
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.
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.
Chromatographic- and/or fluorescence-based lateral flow and membrane-based immunoassays. Some approved rapid influenza diagnostic assays utilize an analyzer reader device.
NP = nasopharyngeal
Rapid molecular assays can provide results in approximately 20 minutes. Alere i Influenza A&B was FDA-cleared for use with both nasal swabs (direct) and NP or nasal swabs in VTM, and CLIA-waived for use with nasal swabs (direct) only. Roche Cobas Influenza A/B was cleared and CLIA-waived by FDA for use with nasopharyngeal swabs only.
Reverse transcription polymerase chain reaction, including FDA-approved test systems, reference laboratory testing using ASR or lab-developed reagents. Some approved molecular assays can produce results in approximately 60-80 minutes.
List may not include all test kits approved by the U.S. Food and Drug Administration. Discontinued tests not included.
Approved respiratory specimens according to manufacturer’s package insert. Note that test performance may vary if other respiratory specimens are used.
Distinguishes between influenza A and B virus infections.
NP = nasopharyngeal.
Does not distinguish between influenza A and B virus infections when used alone.
Disclaimer: Use of trade names or commercial sources is for identification only and does not imply endorsement by the Centers for Disease Control and Prevention or the Department of Health and Human Services.
