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Performance of influenza rapid antigen testing in influenza in emergency department patients
  1. C Biggs1,
  2. P Walsh2,2,3,
  3. C L Overmyer4,
  4. D Gonzalez4,
  5. M Feola4,
  6. E Mordechai4,
  7. M E Adelson4,
  8. K T Iacono4
  1. 1
    Department of Microbiology, The Chester County Hospital, West Chester, Pennsylvania, USA
  2. 2
    Kern Medical Center, Kern County, Bakersfield, California
  3. 3
    David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
  4. 4
    Department of Research and Development, Medical Diagnostic Laboratories, Hamilton, New Jersey, USA
  1. Correspondence to Paul Walsh, Department of Emergency Medicine, Kern Medical Centre, Bakersfield, CA, 93305, USA; yousentwhohome{at}


Background: The use of rapid antigen tests to triage specimens for polymerase chain reaction (PCR) testing from emergency department patients with influenza-like illness during surveillance for novel influenza viruses has been suggested.

Objective: To measure the observed sensitivity and specificity for a widely used rapid antigen test (Binax) using a PCR-based assay (Medical Diagnostic Laboratories).

Methods: Nasopharyngeal samples were taken with flocked swabs (Copan Diagnostics) from patients presenting to the emergency department of a community hospital. Samples were analysed using a rapid antigen and a PCR-based test. PCR testing was used as the criterion reference. Sensitivity and specificity were calculated for influenza and influenza A. Positive predictive values were calculated over a range of possible prevalence.

Results: Samples from 566 unique patients were tested using both methods. Sensitivity was 69.1% (95% CI 58.9% to 78.1%) and specificity was 97.7% (95% CI 95.8% to 98.8%) for the detection of any influenza and 75.3% (95% CI 64.7% to 84.0%) and 97.8% (95% CI 95.9% to 98.9%), respectively, for influenza A only. The resultant positive predictive value ranges from 23% to 77% when the prevalence ranges from 1% to 10%.

Conclusion: When planning early outbreak surveillance, provision of adequate PCR testing capacity rather than triaging specimens using rapid antigen testing for influenza is advisable.

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  • Competing interests None declared.

  • Provenance and Peer review Not commissioned; externally peer reviewed.

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