A-300 Evaluation of Different Storage Conditions of Nasopharyngeal Swabs for the Detection of Influenza A, Influenza B and RSV

Abstract Background Every year, Influenza A (FluA), Influenza B (FluB) and Respiratory Syncytial Virus (RSV) affect our communities and increase the number of patients in our health systems. Molecular techniques, such as real-time PCR have become essential, not only for the diagnostic but also for the epidemiological studies. High amounts of samples or retrospective analysis need the use of samples stored at different conditions. For this reason, a stability study of nasopharyngeal swabs (NP) in Viral Transport Medium (VTM) for FluA, FluB and RSV was performed. Methods Twenty-eight negative FluA, FluB and RSV NP samples in VTM (Vircell, Spain) were used in this study. All samples were mixed into one pool and divided into 7 aliquots. One of them served as a negative control. The others were enriched (each) with different concentrations of viral cultures from ATCC (VR-95PQ™, VR1804PQ™, VR26PQ™) to obtain two positive samples for each pathogen. Samples were stored under specific conditions of time and temperature before being processed: 1 and 2 days stored at 25°C, 3 and 6 days stored at 4°C, and 8, 30 and 180 days stored at −20°C. Each condition was extracted in triplicate with the MagDEA Dx SV kit, using the magLEAD® 12gC instrument (Precision System Science Co.) and analysed with VIASURE SARS-CoV-2, Flu & RSV Real Time PCR Detection Kit (Certest Biotec S.L) in triplicate on CFX96™ Real-Time PCR Detection System (Bio-Rad). The results were compared with the data obtained on the first day (0 h). Results All positive samples were detected in all conditions and matrices. No amplifications were observed in negative samples. There were no major differences compared with the data obtained on the first day. However, a Cq delay of around 1 unit was observed in all pathogens when samples were stored 2 days at 25°C. For this reason, this storage condition would not be recommended. Conclusion NP samples in VTM for the detection of FluA, FluB and RSV can be stored at 25°C for up to 1 day, 4°C for up to 6 days, or frozen at −20°C for up to 180 days.