The objective of COVID-19 testing is to keep a check on the infection rate by quickly identifying both symptomatic and asymptomatic patients to reduce COVID-19 transmission. From the time of pandemic onset in 2021 due to the upcoming COVID strains, testing has been given a lot of priority by supporting the home collection of COVID samples using viral transport medium (VTM kit).
Role of VTM in COVID-19 Testing
The three key phases involved in COVID diagnostics are sample collection and transport (pre-analytical), execution (analytical), and results (post-analytical). VTM kits help in the first phase of sample collection and transportation.
AsCOVID-19 virus (SARS-CoV-2) is an RNA virus, storing samples in the wrong conditions can lead to loss of RNA stability and false-negative results. Therefore, an optimized and validated VTM is crucial for proper collection and transport.
Sample collection starts with collecting human samples with either a nasal or oral swab and placing them inside sterile VTM kit vials. The vials are generally stored at either 2-8°C (short-term storage) or -70°C (long-term storage).
What makes up Viral Transport Medium?
VTM kit has been optimized for preserving the viability of cultures for conducting optimized molecular assay-based testing later. VTM is generally composed of fetal bovine serum (FBS), Hanks’ Balanced Salt Solution (HBSS), antibiotics and antifungals, as well as phenol red. However, several research labs make their own recipe to cater to the different interactions between sample collection devices and vial material.
Fetal Bovine Serum (FBS) has a high concentration of essential components (hormones, transport proteins, and growth factors) for cell survival and proliferation. The serum also promotes antioxidant, cryoprotectant, and anti-adsorption properties. These properties favor keeping the virus-in-solution intact over lysis and thus provide an optimal environment to preserve COVID virus host cells for ensuring quality diagnostic testing. Usually, heat-inactivated FBS is used for preparing VTM.
Hanks’ Balanced Salt Solution (HBSS) helps in providing VTM with an isotonic solution. Antibiotics and antifungals (commonly, gentamicin and amphotericin B) are used as anti-microbial agents to prevent contamination. Phenol red is used as a pH indicator to provide a visual check for contaminants.
How to Use VTM kits?
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