Rapid Molecular Detection and Differentiation of Influenza Viruses A and B

Summary

We describe a rapid, molecular-based Influenza A and B assay. The Influenza assay detects each target within 15 min by employing isothermal amplification with influenza-specific primers followed by target detection with molecular beacon probes. The Influenza A and B assay is user-friendly and required minimal hands-on time to perform.

Abstract

Influenza is a contagious respiratory illness caused by influenza viruses A and B in humans and causes a significant amount of morbidity and mortality every year. The Influenza A and B assay was the first CLIA-waived molecular rapid flu test available. The Influenza A and B test works by employing isothermal amplification with influenza-specific primers followed by target detection with molecular beacon probes. Here, the performance of the Influenza A and B assay on frozen, archived nasopharyngeal swab (NPS) specimens stored in viral transport medium (VTM) were compared to a respiratory panel assay.

The performance of the Influenza A and B assay was evaluated by comparing the results to the respiratory panel reference method. The sensitivity for total influenza virus A was 67.5% (95% CI (CI), 56.6-78.5) and the specificity was 86.9% (CI, 71.0-100). For influenza virus B testing, the sensitivity and specificity were 90.2% (CI, 68.5-100) and 98.8% (CI, 68.5-100), respectively.

This system has the advantage of a significantly shorter test time than any other currently available molecular assay and the simple, pipette-free procedure runs on a fully integrated, closed, small-footprint system. Overall, the Influenza A and B assay evaluated in this study has the potential to serve as a point-of-care rapid influenza diagnostic test.

Introduction

Influenza virus infections result in a significant amount of morbidity and mortality each year^1,2,3. Uncomplicated influenza is characterized by constitutional and respiratory symptoms such as fever, myalgia, headache, and non-productive cough^4,5. Older individuals, young children, immunocompromised patients, and patients with underlying comorbidities are at a higher risk for serious complications such as pneumonia, myocarditis, central nervous system disease, or death^6,

Protocol

ETHICS STATEMENT: The use of left-over clinical specimens is approved and follows the guidelines of the Memorial Sloan Kettering Cancer Center Institutional Review Board.

1. Before Running the Assay

NOTE: The Influenza A and B assay is approved for nasopharyngeal swab specimens and for nasopharyngeal swabs stored in viral transport media. Swabs are included in the kit and should be used for optimal performance. However, rayon, foam, flocked swabs or polyester nasal swabs can also be used to collect nasal swab samples.

1. To collect a nasal swab sample, insert the swab into the nostril that has the most visible drainage or that is most congested.....

Results

In this study, archived NPS specimens were collected from inpatients presenting with influenza-like symptoms at Memorial Sloan-Kettering Cancer Center (MSKCC) during an influenza outbreak between December 15, 2012 and March 1, 2013. The NPS specimens were submitted in 3 ml of VTM and tested as part of routine clinical practice with a molecular assay that detects a panel of respiratory viruses (RP), including Influenza A, A-1, A-3, and B. During the study period, 3,675 NPS specimens were s.......

Discussion

Influenza viruses are significant world-wide causes of morbidity and mortality. Rapid and accurate diagnosis of influenza is one of the major keys to managing flu outbreaks during respiratory season. Other antigen-based tests are rapid and easy to perform; however, they have low sensitivities¹³. On the other hand, traditional molecular tests have improved sensitivity, but require more experienced laboratory technologists to perform and are more costly. The Influenza A and B assay described in this.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Alere i Instrument	Alere	NAT-000 (Global), NAT-024 (US)
Alere i Influenza A & B 24 Test Kit	Alere	425-000 (Global), 425-024 (US)
Alere i Barcode Scanner	Alere	EQ001001
Alere Universal Printer	Alere	55115 (Global), alereiprinter (US)
200 µl precision pipette
200 µl disposable pipette tips
Viral transport medium	Remel	M4-RT