Background: Human influenza virus infections have a world-wide distribution. Seasonal influenza epidemics occur regularly both in the Northern and the Southern hemispheres each winter. These influenza epidemics are estimated to cause approximately 500,000 deaths per year world-wide. The most outstanding characteristic of influenza viruses is their rapid evolution which leads to great variability. This can impact the performance of laboratory diagnostic tests, including nucleic acid amplification tests (NAATs). We investigated the inclusivity of SpeeDx® PlexPCR® RespiVirus assay against contemporary human strains of influenza A and B viruses.
Methods: We conducted in silico analysis of PlexPCR components, namely the target specific PlexZyme and Primer sets, using the international database Global Initiative on Sharing All Influenza Data (GISAID) (https://www.gisaid.org). We analysed influenza strains from 2015-2019 in Europe and Oceania region. The PlexZyme and Primer sets were analysed against the matrix protein (MP) gene of Influenza A and B viruses. We also performed in silico analysis of the same PlexZyme and Primer set against the 2018/2019 vaccine strains. Finally, we performed in vitro studies of the quality assurance samples (QCMD and QAP).
Results: Over 10,000 sequences for human strains of influenza A and B were downloaded and analysed. The PlexZyme and Primer sets were placed in a very conserved region which would not result in false negatives. All strains from 2018/2019 vaccine strains were detected or are expected to be detected based on sequence conservations. Synthetic gene block sequences similar to 2018/2019 vaccine strains were used for in vitro detection. All quality assurance samples from QCMD and QAP were detected using the SpeeDx PlexPCR RespiVirus assay.
Conclusion: The SpeeDx PlexPCR RespiVirus assay detects a wide range of contemporary human influenza viruses. The incorporation of primer sets in a conserved region and inclusion of target specific PlexZymes negates potential false results.