Respiratory Diseases

Diagnosis Diagnostic influenza tests include rapid influenza diagnostic tests (RIDTs), direct fluorescent antibody stains, viral cultures and molecular assays. The tests typically



Influenza Types Identified

Test Time

Viral culture (conventional)

A and B

3-7 days

Rapid culture (shell vial)

A and B

1-3 days


A and B

2-3 hours

distinguish influenza types A from influenza B, and can also identify influenza A subtypes 2009 H1N1, H1, H3, H5, N1, or N2. RIDTs have in routine use since their initial FDA approval in 1999, and they typically detect both Type A and B influenza. They are easy to use, relatively inexpensive, and provide rapid results in 10-30 minutes, allowing physicians to prescribe antivirals in the relatively small Rapid Influenza Diagnostic Tests (antigen) RT-PCR5 (singleplex and multiplex; real-time and other RNA-based) and other molecular assays

A and B

< 30 min

A and B

Varied (generally 1-6 hours)

Source: J Clin Microbiol. 2007 Sep; 45(9): 3109–3110.

window of effectiveness (1-2 days after onset of symptoms). The performance of RIDTs is highly dependent on the quality of the reagents, proficiency of operation, transport and storage

conditions and time from illness onset to sample collection. Many RIDTs detect the nucleoprotein (NP), which is one of the more conserved proteins in the influenza virus and subsequently less likely to undergo mutations that lead to antigenic drift

(which in turn can cause the functional components of an RIDT to not recognize a current influenza strain). The major limitation of currently available RIDTs is their low and variable sensitivity. To obtain a true increase in assay sensitivity, monoclonal antibodies

capable of recognizing existing and emerging strains are critical.


Powered by