Evaluation of a fully automated high-throughput SARS-CoV-2 multiplex qPCR assay with built-in screening functionality for del-HV69/70- and N501Y variants such as B.1.1.7.

BACKGROUND

New SARS-CoV-2 variants with increased transmissibility, like B.1.1.7, first detected in England or B.1.351, first detected in South Africa, have caused considerable concern worldwide. In order to contain the spread of these lineages, it is of utmost importance to have rapid, sensitive and high-throughput detection methods at hand.

METHODS

A set of RT-qPCR assays was modified for a diagnostic SARS-CoV-2 multiplex assay including detection of the del-HV69/70 and N501Y mutations on the cobas6800 platform. Analytical sensitivity was assessed for both wild-type SARS-CoV-2 and B.1.1.7 lineage by serial dilution. For clinical performance, a total of 176 clinical samples were subjected to the test and results compared to a commercial manual typing-PCR assay and next generation sequencing as gold standard.

RESULTS

The multiplex assay was highly sensitive for detection of SARS-CoV-2 RNA in clinical samples, with an LoD of 6.16 cp/ml (CI: 4.00-8.31). LoDs were slightly higher for detection of the HV69/70 deletion (85.92, CI: 61-194.41) and the N501Y SNP (105.99 cp/ml, CI: 81.59 - 183.66). A total of 176 clinical samples were tested with the assay, including 50 samples containing SARS-CoV-2 of the B.1.1.7 lineage, one containing B.1.351 and 85 non-B.1.1.7/B.1.351 lineage, of which three also harbored a HV69/70 deletion. All were correctly identified by the multiplex assay.

CONCLUSION

We describe here a highly sensitive, fully automated multiplex PCR assay for the simultaneous detection of the del-HV69/70 and N501Y mutations that can distinguish between B.1.1.7 and other lineages. The assay allows for high-throughput screening for currently relevant variants in clinical samples prior to sequencing.