The impacts of viral inactivating methods on quantitative RT-PCR for COVID-19

Abstract

ObjectiveThis paper aims to explore the effect of four virus inactivation methods on the rapid detection results of COVID-19 nucleic acid. MethodsCollected samples of nasopharyngeal swabs from 2 patients diagnosed with COVID-19 at the First People's Hospital of Zhaoqing City, each of sample was divided into 5 groups (groupA∼E): A:Non-inactivated raw sample; B:75 % ethanol inactivation; C:56 ℃ incubation for 30 min inactivation; D:65 ℃ incubation for 10 min inactivation; E:Pre-inactivation using RNA virus special preservation fluid added into the sampling tube to treated the nasopharyngeal swab sample separately, using real-time fluorescent RT-PCR to detect the N gene of COVID-19 and the ORF1ab gene simultaneously. All the groups are diluted in 1:2, 1:4, 1:8 ratios. The objectives are to compare the effect of the varied inactivation method on CT(Cycle Threshold)results in PCR, conduct correlation and Bland-Altman analysis. ResultsFor the N gene and ORF1ab gene, the CT values of 4 inactivated and Non-inactivated treatment were correlated (P＜0.001). The results of the four treatment methods and specimens without inactivated treatment have shown good consistency. ConclusionThe treatment of nasopharyngeal swab specimens using mentioned four inactivated methods had no significant effect on the subsequent detection of the new COVID-19 nucleic acid test. Lab test-persons can flexibly adopt pre-inactivation methods to ensure the accuracy of virus nucleic acid test results, meanwhile guarantee the safety of lab test-persons.