Impact of cobas PCR Media freezing on SARS-CoV-2 viral RNA integrity and whole genome sequencing analyses

Abstract

SARS-CoV-2 whole genome sequencing is a molecular biology tool performed to support many aspects of the response to the pandemic. Freezing of primary clinical nasopharyngeal swabs and shipment to reference laboratories is usually required for sequencing. Cobas PCR Media transport medium facilitates high throughput SARS-CoV-2 RT-PCR analyses on cobas platforms. The manufacturer doesn't recommend freezing this transport medium because of risks of degrading molecular templates and impairing test results. Our objective was to compare the quality and results of SARS-CoV-2 genomic sequencing when performed on fresh or frozen samples in cobas PCR Media. Viral genome sequencing was performed using Oxford Nanopore Technologies MinION platform. Sequencing performance, quality and results did not significantly differ between fresh and frozen samples (n = 10). Freezing of cobas PCR Media does not negatively affect SARS-CoV-2 RNA sequencing results and it is therefore a suitable transport medium for outsourcing sequencing analyses to reference laboratories.