Effect of heat inactivation on CT value of realtime RT-PCR technique for SARS-CoV-2 detection

Abstract

SARS-CoV-2 was the cause of the global COVID-19 pandemic in 2019. The cycle threshold (CT) value of the real-time RT-PCR technique is the gold standard in infections diagnosis, infections risk assessment, discharged criteria, and patient isolation for SARS-CoV-2. Heat inactivation is a simple, economical solution for safety in testing for SARS-CoV-2. The change of CT values after heat inactivation has not been thoroughly evaluated. This study evaluated the effect of heat inactivation on CT value in the realtime RT-PCR technique of SARS-CoV-2 detection. Four groups of samples consisted of one non-inactivated group, three groups that were inactivated at 65oC/30min, 80oC/10min, and 95oC/10min; each group included 16 tubes, from 16 nasopharyngeal swabs samples that were confirmed to be infected with SARS-CoV-2. Groups were inactivated and then analysed by realtime PCR technique. The results show that virus inactivation by heat increased the CT value of realtime PCR in SARS-CoV-2 positive samples. The higher temperature was in the inactivation, and the higher CT value was increased.