Evaluation of detection efficiency by SARS-CoV-2 Assay performed on the VitaPCRTM Instrument in samples collected in UTM

ABSTRACT

Background The diagnosis of SARS-CoV-2 infection is essential for the control of the epidemic, the establishment of protecting measures and the therapeutic management of patients. Among diagnostic tests utilizing a real-time reverse transcription polymerase chain reaction (RTPCR) amplification technology, VitaPCRTM SARS-CoV-2 Assay was used in our Laboratory for the rapid qualitative detection and discrimination of SARS-CoV-2 viral RNAs in direct nasopharyngeal (NP) or oropharyngeal (OP) swabs. Aim of the study To test SARS-CoV-2 Assay on NP or OP swabs collected in UTM instead of directly melted in the provided buffer of the kit in order to assess the detection efficiency of the system in relation to the potential interference of UTM in the PCR reaction and to viral RNA concentration. Methods A pool of ten SARS-CoV-2 positive samples collected in UTM, previously tested by quantitative real-time RT-PCR, was assayed on the VitaPCRTM Instrument at several dilutions (from 110 to 1100000) in the provided buffer of the kit, immediately and after a cycle of freezing and thawing at -20°C. Results VitaPCRTM Instrument was able to detect SARSCoV- 2 viral RNA at four out of five tested dilutions, with a good efficiency especially at 110 and 1100 dilutions, while at 11000000 the result was doubtful. After freezing and thawing the detection efficiency sensibly decreased and the Instrument was able to detect the viral RNA only at 110, 1100 and 11000 dilutions, while at 110000 and 11000000 the result was doubtful. Conclusions These preliminary results are promising suggesting the potential use of SARS-CoV-2 Assay on the VitaPCRTM Instrument even with swabs collected in UTM, increasing the versatility of this system. Moreover, the reduced performance of VitaPCRTM Instrument after freezing and thawing the sample suggests a consistent degradation of viral RNA, advising against the use of this type of frozen samples with this assay. Further investigations are recommended.