Influenza A/B

Influenza A/B Swab Test

Influenza is a highly contagious, acute, epidemic to pandemic viral respiratory infection caused by three genera of the Orthomyxoviridaefamily. Influenza virus can be distinguished into influenza virus A, B and C on the basis of antigenic differences between their nucleoprotein and matrix proteins. For types A and B, the antigenic variation of hemagglutinin and neuraminidase is responsible for the emergence of new strains, while type C is antigenically stable.Type A influenza viruses are typically more prevalent than type B viruses and are associated with most serious influenza epidemics, while type B influenza infections are usually milder. Influenza due to type C species is rare compared to types A or B.

Diagnostic tests of influenza available include rapid immunoassay, immunofluorescence assay, polymerase chain reaction (PCR), serology and viral culture. Immunofluorescence assays require staining of specimens immobilized on microscope slides using fluorescent-labeled antibodies for observation by fluorescence microscopy. PCR can only be performed in well equipped laboratory facilities by trained personnel. Serological tests necessitate acute, convalescent blood specimens, and the diagnosis is only retrospective. As the gold standard, traditional culture which employs virus isolation is time-consuming and requires considerable technical expertise.

Rapid immunoassay of influenza A and B has become more important due to the availability of effective antiviral therapy. Rapid diagnosis of influenza can lead to reduced hospital stays, antimicrobial use and cost of hospital care. The Influenza A/B Rapid Test is a lateral flow immunoassay using highly sensitive monoclonal antibodies that are specific for influenza nucleoprotein antigens. The test is specific to influenza A and B antigens with no known cross-reactivity to normal flora or other respiratory pathogens.

Principle

The Influenza A/B Rapid Test detects influenza A and B viral antigens through visual interpretation of color development. Anti-influenza A and B antibodies to the nucleoprotein antigens are immobilized on the test region A and B of the nitrocellulose membrane, respectively. A wash/aspirate or swab sample is added to the sample diluent buffer which is optimized to extract the influenza A or B nucleoprotein antigens from specimen. During testing, the extracted antigens bind to anti-influenza A and B antibodies conjugated to colored particles on the sample pad. As the specimen migrates along the strip by capillary action and interacts with reagents on the membrane, the complex will be captured by either anti-influenza A or anti-influenza B nucleoprotein monoclonal antibodies at the respective detection zone. Excess colored particles are captured at the internal control zone. The presence of a red band in the A and/or B region indicates a positive result for the particular viral antigens, while its absence indicates a negative result. A red band at the control region serves as a procedural control, indicating that the proper volume of specimen has been added and membrane wicking is working.