Effects of storage temperature on throat swabs preserved in different transport media for detection of SARS-CoV-2 by reverse transcriptase polymerase chain reaction

Abstract

Objectives: The coronavirus disease 2019 (COVID-19) pandemic resulted in an increased need for molecular diagnostic testing. Delay in the specimen processing and storage of samples in laboratories leads to degradation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA. Inactivation transport medium (ITM) contains chaotropic agents that inactivate the virus and stabilize SARS-CoV-2 RNA for a longer duration, even at room temperature. The effect of different temperatures and duration of storage of samples in viral transport media (VTM) and ITM for detection of SARS-CoV-2 RNA was assessed. Materials and Methods: Samples from COVID-19 patients were aliquoted in ITM and VTM and kept at ambient temperature, 37°C and 45°C. SARS-CoV-2 viral RNA was extracted. Multiplex real-time polymerase chain reaction was done on days 0, 1, 3, and 5, and cycle threshold (Ct) values were noted. Statistical Analysis: Data were analyzed using the Statistical Package for the Social Sciences version 26.0. Linear variables were summarized as mean and standard deviations. One-way analysis of variance test with post hoc Tukey honestly significant difference was used to compare mean value between different loops and for pair-wise comparison. P < 0.05 was taken as significant. Results: The mean Ct values of both the Orf and E genes of the samples in VTM and ITM were stable across all temperature conditions on day 1. On day 5, the increase in Ct values for both E and Orf genes were significantly higher for VTM than ITM at ambient temperature, 37°C and 45°C. Ribonuclease P failure was significantly higher for VTM than ITM at ambient temperature and 37°C on day 3 and at all temperatures on day 5. Conclusions: ITM is a valuable transport media that can preserve SARS-CoV-2 for up to 5 days at ambient temperature and 37°C. As it renders the samples non-infectious, thus reducing the potential of biohazard events, this transport medium can be used effectively for the collection and transportation of SARS-CoV-2 samples, especially from remote or isolated healthcare facilities.