Rapid Diagnostic Testing for Influenza
Information for Health Care Professionals
Rapid diagnostic tests 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.
- In general, rapid diagnostic testing for influenza should be done when the results will affect clinical decision making.
- Reliability and Interpretation of Rapid Test Results
Reliability and Interpretation of Rapid Test Results
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-positive or false-negative results.
- Sensitivities of rapid diagnostic tests are approximately 50-70% when compared with viral culture or reverse transcription polymerase chain reaction (RT-PCR), and specificities of rapid diagnostic tests for influenza are approximately 90-95%.
- False-positive (and true-negative) results are more likely to occur when disease prevalence in the community is low, which is generally at the beginning and end of the influenza seasons.
- False-negative (and true-positive) results are more likely to occur when disease prevalence is high in the community, which is typically at the height of the influenza season.
Minimize False Results
- Use rapid diagnostic tests with high sensitivity and specificity.
- Collect specimens as early in the illness as possible (within 4-5 days).
- Follow manufacturer’s instructions, including handling of specimens.
- Consider sending specimens for viral culture to confirm results of rapid tests especially when community prevalence of influenza is low and the rapid diagnostic test result is positive and when the rapid diagnostic test result is negative but disease prevalence is high. (Contact your local or state health department for information about influenza activity).
Table 1: Influenza Virus Testing Methods
|Method1||Types Detected||Acceptable Specimens3||Test Time3||CLIA Waived|
|Viral cell culture (conventional)||A and B2||NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum||3-10 days||No|
|Rapid cell culture (shell vials; cell mixtures)||A and B2||As above||1-3 days||No|
|Immunofluorescence, Direct (DFA) or Indirect (IFA) Antibody Staining||A and B2||NP swab or wash, bronchial wash, nasal or endotracheal aspirate||1-4 hours||No|
|RT-PCR4 (singleplex and multiplex; real-time and other RNA-based) and other molecular assays||A and B2||NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum||Varied (Generally 1-6 hours)||No5|
|Rapid Influenza Diagnostic Tests6||A and B||NP swab, (throat swab), nasal wash, nasal aspirate||<30 min.||Yes/No|
- Serologic (antibody detection) testing is not recommended for routine patient diagnosis.
- May be adapted to identification of specific subtypes
- Ref: Leland, et al. 2007, Clin Micro Rev 20: 49-78. Approved respiratory specimens vary among FDA cleared influenza assays.
- Reverse transcriptase polymerase chain reaction, including FDA-approved test systems, reference laboratory testing using ASR or lab-developed reagents
- Random-access, single cartridge tests may be moderately complex
- Immunochromatographic lateral flow and membrane-based immunoassays
Table 2: Characteristics of Rapid Influenza Diagnostic Tests1
|Approved Specimens1||Test Time|
|3M™ Rapid Detection|
Flu A+B Test4,6
|A and B||NP2 swab/aspirate|
|BD Veritor System for Rapid Detection of Flu A+B5,6,8|
|A and B||NP2 swab/nasal swab||10 minutes|
|BinaxNOW® Influenza A&B5,6|
|A and B||NP2 swab|
|BioSign® Flu A+B4,6|
|A and B||NP2 swab/aspirate/wash, nasal swab||15 minutes|
|Clearview® Exact Influenza A & B4,6|
|A and B||Nasal swab||15 minutes|
|Directigen™ EZ Flu A+B4,6|
|A and B||NP2 wash/aspirate/swab|
|OSOM® Influenza A&B4,6|
|A and B||Nasal swab||10 minutes|
|QuickVue® Influenza Test3,5|
|A or B||Nasal wash/aspirate/swab||10 minutes|
|QuickVue® Influenza A+B Test5,6|
|A and B||NP2 swab|
|SAS™ FluAlert A&B4,6|
|A and B||Nasal wash/aspirate||15 minutes|
|SAS™ FluAlert A3,5|
|A only||Nasal wash/aspirate||15 minutes|
|SAS™ FluAlert B3,5|
|B only||Nasal wash/aspirate||15 minutes|
|Sofia Influenza A+B 4,6,7,8|
|A and B||NP2 aspirate/swab/wash|
|A and B||NP2 aspirate/swab|
|XPECT™ Flu A&B4,6|
|A and B||Nasal wash/swab|
- 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.
- NP = nasopharyngeal.
- Does not distinguish between influenza A and B virus infections when used alone.
- Moderately complex test – requires specific laboratory certification.
- CLIA-waived test. Can be used in any office setting. Requires a certificate of waiver or higher laboratory certification.
- Distinguishes between influenza A and B virus infections.
- Immunofluorescence assay.
- Requires use of a separate analyzer reader device.
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.