Performance Evaluation of SARS-CoV-2 Viral Transport Medium Produced by Bangladesh Reference Institute for Chemical Measurements

Abstract

A viral transport medium (VTM) was developed following the Centers for Disease Control and Prevention, USA (US-CDC) standard operating procedure (SOP) DSR-052-05 with necessary improvisation and was used for storing coronavirus disease 2019 (COVID-19) swab specimens. Considering Bangladesh's supply chain and storage conditions, improvisation was essential for extending sample storage time while retaining efficiency. In-house VTM was produced using Hank's balanced salt solution (HBSS) supplemented with 1% bovine serum albumin V (BSA), 0.5 µg /mL of gentamicin sulfate, and 100 µg/mL of fluconazole. The produced VTM composition, quality, sterility, specificity, and efficiency were verified in-house and through an independent contract research organization (CRO). An accelerated stability study projected that under the recommended temperature (4 °C), it would remain stable for four months and preserve samples for over a month. The real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) test detected the targeted N gene and ORF1ab gene from the VTM stored samples. Our VTM is equally as effective as the Sansure Biotech VTM in keeping SARS-CoV-2 RNA specimens detectable in rRT-PCR (100% sensitivity and specificity in random and blinded samples). In conclusion, the BRiCM VTM will make the battle against pandemics easier by effectively collecting and storing nasopharyngeal and oropharyngeal swabs for COVID-19 detection.

Keywords: Hank’s balanced salt solution (HBSS); N gene; coronavirus disease 2019 (COVID-19); rRT-PCR; viral transport medium (VTM).

Figure 1

Schematic diagram of BRiCM VTM production workflow. The figure shows the steps in a continuous workflow diagram of the VTM preparation and packaging steps (italicized with bold numbering). Processes in the green-shaded area were performed in the sterile cabinet.

Figure 2

LC-MS scan of VTM. LC-MS scan of VTM for fluconazole (A) and gentamicin sulfate (B) identification.

Figure 3

Extent of SARS-CoV-2 RNA detection over 14 days. Ct values of N gene (A) and ORF gene (B) amplification from the delayed nucleic acid amplification test (NAAT) plotted in the Levey-Jennings plot. The test days with more than one data point represent the same batch of VTM evaluated for multiple samples. Other than two specimens, deviation in Ct values for both viral RNA and control gene amplification was within the limit of variation, i.e., 2σ.