Rapid Diagnostic Testing for Influenza: Information for Health Care Professionals
On this Page
- Background
- Reliability and Interpretation of Rapid Test Results
- Minimize False Results
- Table 1: Influenza Virus Testing Methods
- Table 2: Characteristics of Rapid Influenza Diagnostic Tests
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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
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-positive or false-negative 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)
- 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 season.
- 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 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 tests especially when community influenza activity is low and the rapid diagnostic test result is positive and when the rapid diagnostic test result is negative but influenza activity is high. (Contact your local or state health department for information about influenza activity).
Table 1: Influenza Virus Testing Methods
| Method1 | Types Detected | Acceptable Specimens2 | Test Time | CLIA Waived3 |
|---|---|---|---|---|
| Viral cell culture (conventional) | A and B | NP4 swab, throat swab, NP2 or bronchial wash, nasal or endotracheal aspirate, sputum | 3-10 days | No |
| Rapid cell culture (shell vials; cell mixtures) | A and B | As above | 1-3 days | No |
| Immunofluorescence, Direct (DFA) or Indirect (IFA) Antibody Staining [antigen detection] | A and B | NP4 swab or wash, bronchial wash, nasal or endotracheal aspirate | 1-4 hours | No |
| RT-PCR5 (singleplex and multiplex; real-time and other RNA-based) and other molecular assays | A and B | NP4 swab, throat swab, NP2 or bronchial wash, nasal or endotracheal aspirate, sputum | Varied (Generally ≤15 minutes-6 hours)7 | No |
| Rapid Molecular Assay | A and B | NP4 swab, nasal aspirate, wash, swab | ≤15 minutes7 | Yes/No7 |
| Rapid Influenza Diagnostic Tests6 (antigen detection) | A and B | NP4 swab, (throat swab), nasal wash, nasal aspirate | <30 min. | Yes/No |
- Serologic (antibody detection) testing is not recommended for routine patient diagnosis.
- Ref: Leland, et al. 2007, Clin Micro Rev 20: 49-78. Approved respiratory specimens vary among FDA cleared influenza assays.
- Ref: http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/index.html
- NP = nasopharyngeal
- Reverse transcriptase polymerase chain reaction, including FDA-approved test systems, reference laboratory testing using ASR or lab-developed reagents
- Chromatographic- and/or fluorescence-based lateral flow and membrane-based immunoassays
- Rapid molecular assays can provide results in 15 minutes or less. Alere i Influenza A&B was cleared by FDA for nasal swabs and viral transport media. Alere i Influenza A&B was CLIA-waived only for use with nasal swabs.
Table 2: Characteristics of Rapid Influenza Diagnostic Tests1
| Procedure (Manufacturer/Distributor) | Influenza Virus Types Detected | Approved Specimens2 | CLIA Waived3 | Uses Analyzer Reader Device |
|---|---|---|---|---|
| Alere™ i Influenza A/B (Alere Scarborough, Inc.) | A and B | Nasal swab (in VTM8) | No | Yes |
| Alere™ i Influenza A/B4 (CLIA Waived) (Alere Scarborough, Inc.) | A and B | Nasal swab (Direct) | Yes | Yes |
| BD Directigen™ EZ Flu A+B4 (Becton-Dickinson & Co.) | A and B | NP5 wash/aspirate/swab Throat swab | No | No |
| BD Veritor™ System for Rapid Detection of Flu A+B4 (CLIA-waived), (Becton Dickinson & Co.) | A and B | NP5 swab/ nasal swab | Yes | Yes |
| BD Veritor™ System for Rapid Detection of Flu A+B4 (Moderately Complex), (Becton Dickinson & Co.) | A and B | NP5 wash/aspirate | No | Yes |
| Binax NOW® Influenza A&B4 Test (Binax, Inc.) | A and B | NP5 swab, Nasal wash/aspirate/swab | Yes | No |
| BioSign® Flu A+B4 or OraSure QuickFlu Rapid A+B Test or Polymedco Poly stat Flu A&B Test or LifeSign LLC Status Flu A&B (Princeton BioMedtech Corp.) | A and B | NP5 swab/aspirate/wash, nasal swab | No | No |
| ClearView Exact II Influenza A&B Test or Alere Influenza A&B Test (Binax d/b/a Inverness Medical Alere Scarborough, Inc.) | A and B | Nasal swab | Yes | No |
| Genzyme OSOM® Influenza A&B4 Test (Genzyme Corp.) | A and B | Nasal swab | No | No |
| QuickVue® Influenza A/B Test6 (Quidel Corp.) | A and B | Nasal wash/aspirate/swab | Yes | No |
| QuickVue® Influenza A+B Test4 (Quidel Corp.) | A and B | NP5 swab Nasal wash/aspirate/swab | Yes | No |
| RAMP Influenza A/B Assay or 3M™ Rapid Detection Flu A+B Test4 (Response Biomedical Corp.) | A and B | NP5 swab/aspirate Nasal wash/aspirate | No | Yes |
| SAS™ FluAlert A&B Test (SA Scientific, Inc.) | A and B | Nasal wash/aspirate | No | No |
| SAS™ Influenza A4 Test (SA Scientific, Inc.) | A only | Nasal wash/aspirate | Yes | No |
| SAS™ Influenza B6 Test (SA Scientific, Inc.) | B only | Nasal wash/aspirate | Yes | No |
| Sofia® Analyzer and Influenza A+B FIA (CLIA-waived) (Quidel Corp.) | A and B | NP5 swab Nasal swab | Yes | Yes |
| Sofia® Analyzer and Influenza A+B4,7, FIA (Quidel Corp.) | A and B | NP5 aspirate/swab/wash Nasal swab | No | Yes |
| TRU FLU®4 (Meridian Bioscience, Inc.) | A and B | NP5 aspirate/swab Nasal wash/swab | No | No |
| XPECT™ Influenza A/B4 (Remel Inc./Thermo Fisher Scientific) | A and B | Nasal wash/swab Throat swab | No | No |
- 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.
- Ref: http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/index.html
- Distinguishes between influenza A and B virus infections.
- NP = nasopharyngeal.
- Does not distinguish between influenza A and B virus infections when used alone.
- Requires use of a separate analyzer reader device.
- VTM = viral transport media
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