Managing Influenza with

Diagnostic Resources

Rapid influenza diagnostic tests (RIDTs) can identify the presence of influenza A and B viruses, and display the result in a qualitative way (positive vs. negative), in as little as ten minutes. RIDTs may also be used to help with diagnostic and treatment decisions for patients in clinical settings, such as whether to prescribe antiviral medications. Additionally, positive RIDT results from one or more ill persons with suspected influenza can support decisions to promptly implement prevention and control measures for influenza outbreaks in institutions (i.e., nursing homes, chronic care facilities, and hospitals), camps, schools, and other settings.

When is use of RIDTs beneficial?

  • Testing during an outbreak of acute respiratory disease can determine if influenza is the cause
  • During the flu season, testing select patients with respiratory illnesses compatible with flu can help;
    • Identify whether influenza is present in a specific patient population
    • Healthcare providers determine how to use their clinical judgment for diagnosing and treating respiratory illness.

 


Influenza Virus Testing Methods

Method1

Virus 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

NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, sputum

1-3 days

No

Immunofluorescence
[Direct Fluorescent
Antibody (DFA) or
Indirect Fluorescent
Antibody (IFA) 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)

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

Less than 30 minutes

 

  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. Immunochromatographic lateral flow and membrane-based immunoassays

Source: CDC “Guidance for Clinicians on the Use of Rapid Influenza Diagnostic Tests for the 2010-2011 Influenza Season,” Page last updated: July 29, 2011

 

The importance of laboratory-based surveillance:
Laboratory-based surveillance for flu virus is critically important to the selection of viruses for the next season's influenza vaccine. This data is also useful for obtaining information on the emergence and prevalence of antiviral resistant strains, and the identification of human infection with novel influenza A virus (e.g. an influenza A virus of animal origin that may occasionally cause illnesses in people) that may have pandemic potential.

 

RESOURCES