Incidence of Non Amplification of N Gene of SARS-CoV-2 using Commercially Available Real Time Polymerase Chain Reaction Kit and its Comparison with Two Other Different Kits

Introduction: Novel Coronavirus Disease-2019 (COVID-19) caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in an unprecedented global pandemic. Real Time Polymerase Chain Reaction (RT-PCR) tests are being used in the diagnosis of COVID-19 worldwide however mutations in the SARS-CoV-2 genome have generated many SARS-CoV-2 genome variants and which may affect the correct Reverse transcriptase-Real time Polymerase Chain Reaction (RT-PCR) diagnosis.

Aim: To confirm and study the incidence of the non amplification of the SARS-CoV-2 Nucleocapsid gene (N gene) target among known SARS-CoV-2 positive samples.

Materials and Methods: This retrospective observational study was carried out at the State Virology Laboratory, Gandhi Medical College, Bhopal, Madhya Pradesh, India, during January to May 2021. During the study period, a total of 159 SARS-CoV-2 positive samples were failed to amplify the N gene target. To investigate the non amplification of N gene target of SARS-CoV-2, a total of 20 samples were selected and retested using the initially used RT-PCR kit (VIRALDTECT RT-PCR kit) and also with the two different RT-PCR kits (TaqPath RT-PCR kit and Hi-PCR RT-PCR kit) which also contain primers/probes for the SARS-CoV-2 N gene target.

Results: Amplification and detection of the SARS-CoV-2 N target gene was not observed in VIRALDTECT RT-PCR test results. In contrast, amplification was detected in the N gene target of SARS-CoV-2 while using the TaqPath and Hi-PCR kits. Obtained results confirm the failure of the annealing of VIRALDTECT kit N gene primer/probe and suggest the possible mutation event in the SARS-CoV-2 N gene among the N gene non amplified samples.

Conclusion: Present study reports, the incidence of non amplification of SARS-CoV-2 N gene, where the RT-PCR kit failed to detect N gene target and seriously affect RT-PCR diagnosis. Hence, the study emphasises the revalidation of commercially available SARS-CoV-2, RT-PCR kits to identify these kinds of failure incidence.