Thermal inactivation of COVID-19 specimens improves RNA quality and quantity

The rapid spread of coronavirus disease 2019 (COVID-19), a disease caused by severe acute respiratory syndrome coronavirus 2, poses a huge demand for immediate diagnosis. Real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) of nasopharyngeal (NP) and oropharyngeal (OP) swabs have been used to confirm the clinical diagnosis. To avoid the risk of viral-exposure of laboratory workers, thermal inactivation is currently recommended but has unknown effects on the accuracy of the rRT-PCR results. Thirty-six NP/OP specimens were collected from COVID-19 patients and subjected to thermal inactivation (60°C for 30 min) or the RNA extraction processes to activate the form. Here, our data showed that the concentration of extracted-RNA increases upon thermal inactivation compared to the active form (p = .028).  Significantly higher levels of RNA copy number were obtained in inactivated compared to the active samples for both N and ORF1ab genes (p = .009, p = .032, respectively). Thermal inactivation elevated concentration and copy number of extracted-RNA, possibly through viral-capsid degradation and/or nucleoprotein denaturation.