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Rapid Diagnostic Testing for Influenza: Information for Health Care Professionals

Background

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
Method1Types DetectedAcceptable Specimens3Test Time3CLIA Waived
Viral cell culture (conventional)A and B2NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum3-10 daysNo
Rapid cell culture (shell vials; cell mixtures)A and B2As above1-3 daysNo
Immunofluorescence, Direct (DFA) or Indirect (IFA) Antibody StainingA and B2NP swab or wash, bronchial wash, nasal or endotracheal aspirate1-4 hoursNo
RT-PCR4 (singleplex and multiplex; real-time and other RNA-based) and other molecular assaysA and B2NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputumVaried (Generally 1-6 hours)No5
Rapid Molecular Assays6A and BNasal swab15 min.No
Rapid Influenza Diagnostic Tests7A and BNP swab, (throat swab), nasal wash, nasal aspirate<30 min.Yes/No
  1. Serologic (antibody detection) testing is not recommended for routine patient diagnosis.
  2. May be adapted to identification of specific subtypes
  3. Ref: Leland, et al. 2007, Clin Micro Rev 20: 49-78. Approved respiratory specimens vary among FDA cleared influenza assays.
  4. Reverse transcriptase polymerase chain reaction, including FDA-approved test systems, reference laboratory testing using ASR or lab-developed reagents
  5. Random-access, single cartridge tests may be moderately complex
  6. Isothermal nucleic acid amplication. As of June 2013, there is only one FDA-approved rapid molecular assay.
  7. Immunochromatographic lateral flow and membrane-based immunoassays
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Table 2: Characteristics of Rapid Influenza Diagnostic Tests1
Procedure
(Manufacturer/Distributor)
Influenza Virus
Types Detected
Approved Specimens1Test TimeCLIA Waved
3M™ Rapid Detection
Flu A+B Test4,5
(3M)
A and BNP2 swab/aspirate
Nasal wash/aspirate
15 minutesNo
Alere Influenza A & B5
(Alere)
A and BNasal swab15 minutesYes
BD Veritor System for Rapid Detection of Flu A+B CLIA-waived5,7
(Becton Dickinson)
A and BNP2 swab/nasal swab10 minutesYes
BD Veritor System for Rapid Detection of Flu A+B Moderately Complex4,5,7
(Becton Dickinson)
A and BNP2 wash/aspirate/swab10 minutesNo
BinaxNOW® Influenza A&B5
(Alere)
A and BNP2 swab,
Nasal wash/aspirate/swab
15 minutesYes
BioSign® Flu A+B4,5
(Princeton BioMedtech)
A and BNP2 swab/aspirate/wash, nasal swab15 minutesNo
Directigen™ EZ Flu A+B4,5
(Becton-Dickinson)
A and BNP2 wash/aspirate/swab
Throat swab
15 minutesNo
OSOM® Influenza A&B4,5
(Sekisui Diagnostics)
A and BNasal swab10 minutesNo
QuickVue® Influenza Test3
(Quidel)
A or BNasal wash/aspirate/swab10 minutesYes
QuickVue® Influenza A+B Test5
(Quidel)
A and BNP2 swab
Nasal wash/aspirate/swab
10 minutesNo
SAS™ FluAlert A&B4,7
(SA Scientific)
A and BNasal wash/aspirate15 minutesYes
SAS™ FluAlert A3
(SA Scientific)
A onlyNasal wash/aspirate15 minutesYes
SAS™ FluAlert B3
(SA Scientific)
B onlyNasal wash/aspirate15 minutesYes
Sofia Influenza A+B 5,6,7
(Quidel)
A and BNP2 aspirate/swab/wash
Nasal wash
15 minutesYes
TRU FLU®4,5
(Meridian Bioscience)
A and BNP2 aspirate/swab
Nasal wash
15 minutesNo
XPECT™ Flu A&B4,5
(Remel/Thermofisher)
A and BNasal wash/swab
Throat swab
15 minutesNo
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  1. 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.
  2. NP = nasopharyngeal.
  3. Does not distinguish between influenza A and B virus infections when used alone.
  4. Moderately complex test – requires specific laboratory certification.
  5. Distinguishes between influenza A and B virus infections.
  6. Immunofluorescence assay.
  7. 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.

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