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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.

Introduction: The whole world is facing an ongoing global health emergency of COVID-19 disease caused by the SARS-CoV-2. Real-Time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) is a gold standard in the detection of SARS-CoV-2 infection. Presently, many single tube multiple gene target RTPCR kits have been developed and are commercially available for Corona Virus Disease 2019 (COVID-19) diagnosis. Aim: To evaluate the performance of seven COVID-19 RT-PCR kits (DiagSure, Meril, VIRALDTECT II, TruPCR, Q-line, Allplex and TaqPath) which are commercially available for COVID-19 RT-PCR diagnosis. Materials and Methods: This observational study was conducted at the State Virology Laboratory (SVL), Gandhi Medical College, Bhopal, Madhya Pradesh, India. Seven commercially available kits have been evaluated on the basis of: (i) number of SARS-CoV-2 specific gene target; (ii) human housekeeping genes as internal control; (iii) RT-PCR run time; and (iv) kit performances to correctly detect SARS-CoV-2 positive and negative RNA samples. A total of 50 RNA samples (left over RNA) were included, master mix preparation, template addition and RT-PCR test has been performed according to kits literature. At the end of PCR run, mean and standard deviation of obtained cut-off of all kits were calculated using Microsoft Excel. Results: All seven RT-PCR kits performed satisfactory regarding the reproducibility and they could correctly identify 30 positive and 20 negative RNA samples. RNA samples (group C) having low viral loads with a high Cycle threshold (Ct) value (>30) were also detected by all these seven kits. Obtained Ct values of each group was in parallel range in comparison with the initial testing Ct values. Kits were found to be superior which contains primers and probes for three SARS-CoV-2 specific gene targets, have human housekeeping gene as internal control and taking less time to complete RT-PCR. Conclusion: All seven COVID-19 RT-PCR kits included in this study demonstrated satisfactory performance and can be used for the routine molecular diagnosis of COVID-19 disease.