Evaluation of Viral Transport Medium and Inactivation Transport Medium Under Different Storage Conditions for the...

Accurate and timely diagnosis is vital for the surveillance and containment of COVID-19. Traditional viral transport medium (VTM) for sample collection requires strict cold chain maintenance, which poses biosafety and logistical challenges, especially in resource-limited or remote settings. Inactivation transport medium (ITM), containing guanidinium thiocyanate, is designed for safe, room temperature (RT) transport. This study compared ITM with VTM for RNA stability and diagnostic efficiency using the cobas® 8800 system.

In this comparative observational study, oropharyngeal swabs were collected from 80 SARS-CoV-2-positive patients and 20 healthy controls. For each participant, three swabs were collected: one for ITM and two for VTM. Samples in ITM were stored at RT (25-32 °C), and those in VTM at 4 °C and RT. All samples were tested by reverse transcription quantitative polymerase chain reaction (RT-qPCR) (cobas® 8800) on days zero, one, two, and three. Cycle threshold (Ct) values for ORF1a/b and E genes were compared across groups to assess RNA stability and detection efficiency.

Ct values remained stable across ITM and VTM at 4 °C for up to 72 hours, while VTM at RT showed a trend of higher Ct values, particularly by day three. Although not statistically significant, degradation was more evident in VTM at RT. A significant difference was observed for the E gene on day one (p = 0.001), favouring ITM. Negative controls remained consistently negative across all media and temperatures.

ITM provides RNA preservation and diagnostic performance for SARS-CoV-2 detection comparable to VTM, with the added benefits of RT stability and enhanced biosafety. Use of ITM may eliminate the need for cold chain logistics and reduce biohazard risks, improving the reliability and flexibility of COVID-19 testing in varied settings.