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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.

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 of illness onset).
  • Follow manufacturer’s instructions, including handling of specimens, as described in the device package insert.
  • Consider sending specimens for viral culture or RT-PCR 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 Specimens2Test TimeCLIA Waived3
Viral cell culture (conventional)A and BNP4 swab, throat swab, NP2 or bronchial wash, nasal or endotracheal aspirate, sputum3-10 daysNo
Rapid cell culture (shell vials; cell mixtures)A and BAs above1-3 daysNo
Immunofluorescence, Direct (DFA) or Indirect (IFA) Antibody StainingA and BNP4 swab or wash, bronchial wash, nasal or endotracheal aspirate1-4 hoursNo
RT-PCR5 (singleplex and multiplex; real-time and other RNA-based) and other molecular assaysA and BNP4 swab, throat swab, NP2 or bronchial wash, nasal or endotracheal aspirate, sputumVaried (Generally 1-6 hours)No
Rapid Influenza Diagnostic Tests6 (antigen)A and BNP4 swab, (throat swab), nasal wash, nasal aspirate<30 min.Yes/No
  1. Serologic (antibody detection) testing is not recommended for routine patient diagnosis.
  2. Ref: Leland, et al. 2007, Clin Micro Rev 20: 49-78. Approved respiratory specimens vary among FDA cleared influenza assays.
  3. Ref: http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/index.html
  4. NP = nasopharyngeal
  5. Reverse transcriptase polymerase chain reaction, including FDA-approved test systems, reference laboratory testing using ASR or lab-developed reagents
  6. Chromatographic- and/or fluorescence-based 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 Specimens2CLIA Waved3
3M™ Rapid Detection
Flu A+B Test4
(3M)
A and BNP5 swab/aspirate
Nasal wash/aspirate
No
Alere™ Influenza A & B4
(Alere)
A and BNasal swabYes
BD Veritor™ System for Rapid Detection of Flu A+B CLIA-waived4,8
(Becton Dickinson)
A and BNP5 swab/nasal swabYes
BD Veritor™ System for Rapid Detection of Flu A+B Moderately Complex4,8
(Becton Dickinson)
A and BNP5 wash/aspirate/swabNo
BinaxNOW® Influenza A&B4
(Alere)
A and BNP5 swab,
Nasal wash/aspirate/swab
Yes
BioSign® Flu A+B4

(Princeton BioMedtech)
A and BNP5 swab/aspirate/wash, nasal swabNo
Directigen™ EZ Flu A+B4
(Becton-Dickinson)
A and BNP5 wash/aspirate/swab
Throat swab
No
OSOM® Influenza A&B4
(Sekisui Diagnostics)
A and BNasal swabNo
QuickVue® Influenza Test6
(Quidel)
A or BNasal wash/aspirate/swabYes
QuickVue® Influenza A+B Test4
(Quidel)
A and BNP5 swab
Nasal wash/aspirate/swab
Yes
SAS™ FluAlert A&B
(SA Scientific)
A and BNasal wash/aspirateNo
SAS™ FluAlert A4
(SA Scientific)
A onlyNasal wash/aspirateYes
SAS™ FluAlert B6
(SA Scientific)
B onlyNasal wash/aspirateYes
Sofia® Influenza A+B 4,7,8
(Quidel)
A and BNP5 aspirate/swab/wash
Nasal wash
Yes
TRU FLU®4
(Meridian Bioscience)
A and BNP5 aspirate/swab
Nasal wash
No
XPECT™ Flu A&B4
(Remel/Thermofisher)
A and BNasal wash/swab
Throat swab
No
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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.
  2. Approved respiratory specimens according to manufacturer's package insert. Note that test performance may vary if other respiratory specimens are used.
  3. Ref: http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/index.html
  4. Distinguishes between influenza A and B virus infections.
  5. NP = nasopharyngeal.
  6. Does not distinguish between influenza A and B virus infections when used alone.
  7. Immunofluorescence assay.
  8. 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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