Evaluation of the use of VitaPCRTM SARS-CoV-2 Assay for the confirmation of samples tested positive with LIAISON SARS-CoV-2 Ag assay

ABSTRACT

Background At the Urbino hospital, all patients tested with antigen tests for SARS-CoV-2, if positive, are confirmed with a molecular test. Among the molecular tests in use in our laboratory, VitaPCRTM SARS-CoV-2 Assay is the fastest and easiest to use, as it takes about half an hour from preparation to the result and does not require a biosecurity laboratory, because performed from inactivated samples. Aim of the study Given the rapidity of VitaPCRTM SARS-CoV-2 Assay, it was decided to use it for the confirmation of samples found positive to LIAISON SARS-CoV-2 Ag test. This last test is performed by dedicated tubes with inactivating buffer based on detergent, therefore it does not interfere in the processes of extraction and amplification of nucleic acids. Materials and methods For evaluation, 48 samples tested positive with LIAISON SARS-CoV-2 Ag (Diasorin) test were analyzed, coming from various departments of the Urbino hospital, and confirmed by SimplexaTM COVID-19 Direct (Diasorin) molecular test. From the tubes of all the samples, 200 uL were taken and transferred to dedicated tubes for analysis with VitaPCRTM SARS-CoV-2 Assay (Menarini) to be analyzed, after eliminating 2.2 mL of buffer. Results VitaPCRTM SARS-CoV-2 Assay was able to detect SARSCoV- 2 RNA in all 48 tested antigenically positive samples. In particular, even in all positive samples with low values of TCID50/mL (<1000), 11 out of 48, results with Ct<28.8 were found, although not maintaining a direct correspondence between quantity of antigen and quantity of detected RNA. Conclusions The results obtained, despite requiring an increase in the number of cases, demonstrate the potential use of VitaPCRTM SARS-CoV-2 Assay for the confirmation of positive samples directly from the inactivated buffer used for LIAISON SARS-CoV-2 Ag assay. VitaPCRTM instrument, given the speed, simplicity of use and the possibility of use outside biosafety laboratories, it is an excellent diagnostic tool to support the confirmation procedures of samples tested positive for the SARSCoV- 2 N antigen.