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Influenza A and B Antigen, Immunoassay

Test code(s) 11177

This test uses a rapid, qualitative immunoassay method that detects antigen associated with viable and nonviable influenza A and B viruses. The assay differentiates between A and B viruses, but cannot differentiate subtypes. It can be performed using nasal washes or swabs and throat swabs. It has not been validated for use in monitoring antiviral therapy.

In various manufacturer studies, the sensitivity ranged from 37% to 100%. The specificity ranged from 40% to 100%.1 Although the turnaround time is rapid, other methods may provide more sensitive and specific results.

An inadequate specimen (eg, insufficient nasal or pharyngeal exudate), a low level of viral shedding, and improper specimen transport may cause false-negative results.

A positive result means an influenza A and/or B antigen was detected. The antigen may or may not be associated with clinical symptoms. A positive result does not exclude coinfection with additional pathogens.



  1. Henrickson, Kelly. Advances in the laboratory diagnosis of viral respiratory disease. Pediatr Infect Dis J. 2004;23:S6-10.
  2. Weinberg A, Walker ML. Evaluation of three immunoassay kits for rapid detection of influenza virus A and B.Clin Diagn Lab Immunol. 2005;12:367-370.


This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.


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