Finding respiratory viruses in nasopharyngeal aspirates: comparison between direct immunofluorescence and a new multiplex PCR method

Abstract number: S474

Jemielity S., Barbani M., Staub T., Grandgirard D., Gorgievski-Hrisoho M.

Respiratory viruses are among the most frequent human pathogens worldwide, leading to a significant number of hospitalisations, especially in children and in immune-compromised patients. Several new diagnostics tools for respiratory viruses have recently appeared on the market, including the xTag Respiratory Viral Panel (RVP) by Luminex Molecular Diagnostics. The goal of the present study was to compare this new multiplex PCR method with conventional direct immunofluorescence (DIF) in children's nasopharyngeal aspirates for the following viruses: respiratory sincytial virus (RSV), adenovirus (ADV), parainfluenza viruses 1–3 (PIF), influenza viruses A and B (IF), as well as human metapneumovirus (hMPV). The RVP kit permits in addition the detection of entero-/rhinoviruses, coronaviruses and parainfluenza virus 4.

In total 240 nasopharyngeal aspirates (126 DIF negative and 114 DIF positive samples) were analysed. All RSV, PIVA, IF and hMPV DIF positive samples (43, 15, 18 and 11, respectively) were confirmed as positive for the same virus by RVP. For ADV, however, only 13 out of 27 DIF positive samples (48%) were also ADV positive by RVP. The samples with discrepant results are currently being reanalysed by DIF and by a second, independent PCR.

Of note is the finding that over 64% (81/126) of all DIF negative samples were positive when analysed with RVP. This was in great part due to the additional entero-/rhinoviruses detected by RVP (75/81), but also because of additional RSV, IF, PIF, ADV and hMPV positive samples that had been missed with the DIF assays (21/81). Finally, using RVP we detected as many as 10.4% (25/240) of double and 0.5% (1/240) of triple infections, versus a single double infection detected by DIF. The implications of our findings for both diagnostics as well as clinical practices are discussed.