Evaluation of Saline as Potential Alternative to Viral Transport Media for COVID-19 Samples Stored at Different Temperatures
Dr. Nitya Vyas,
Senior Professor and Head, Department of Microbiology, Sawai Man Singh Medical
College, Jaipur, Rajasthan, India.
Introduction: Severe acute respiratory syndrome coronavirus-2 (SARS CoV 2) virus, a causative agent of COVID-19 has led to universal pandemic. During this pandemic there has been an acute shortage of good quality Viral Transport Medium (VTM) because of increase in number of infected people worldwide. It is also difficult to maintain the transport and storing conditions in line with the guidelines in pandemics.
Aim: To assess the feasibility of Oropharyngeal Swab (OP)/Nasal swabs in 0.9% normal saline in place of VTM and to analyse the effect of temperature on nucleic acid detection by rRT PCR on saline samples stored at 4°C, ambient and at higher temperature (37°C).
Materials and Methods: The present study was an observational analytical study which included 94 positive and 5 negative samples. Patients' nasal or OP samples were collected as dry swabs and in VTM. Normal saline was added once the samples were received in the laboratory. PCR was done with saline and VTM samples both on day 1. Samples were aliquotted in 3 sets and one set was kept at 4°-8° C and other two at 25°C and 37°C, respectively. All positive samples were further tested on day 3, day 4 and day 6. Results were analysed and compared.
Results: Samples in normal saline showed very good sensitivity at all temperatures (4°-8°C, 25°C and 37°C) till day 6. Both the swab samples (in saline and in VTM) showed nearly 100% agreement in rRT-PCR results. Ct value variation was also ≤±2.
Conclusion: Looking into the cost and logistics issues especially during pandemics, saline is a good and cheaper alternative to VTM and with its use, testing capacity can be expanded.