key: cord-0769853-2skb43f2 authors: Steinlin-Schopfer, Jacqueline; Barbani, Maria Teresa; Kamgang, Richard; Zwahlen, Martina; Suter-Riniker, Franziska; Dijkman, Ronald title: Evaluation of the Roche Antigen Rapid Test and a Cell Culture-Based Assay compared to rRT- PCR for the detection of SARS CoV-2: a contribution to the discussion about SARS CoV-2 diagnostic tests and contagiousness date: 2021-05-09 journal: Journal of clinical virology plus DOI: 10.1016/j.jcvp.2021.100020 sha: e332a7a31794c4edf24eec15f97577a29e095e5a doc_id: 769853 cord_uid: 2skb43f2 Background: The most sensitive method to detect SARS-CoV-2 relies on rRT-PCR; however, viral RNA can be detected weeks/months after clinical resolution. Since rRT-PCR cannot discern between non- and infectious virus, it is unclear whether the presence of viral RNA after recovery reflects infectious SARS-CoV-2. However, recent studies suggest a positive correlation between antigen rapid tests (Ag-RDT) and virus isolation that is more suited to assess contagiousness. Objectives: To assess the utility of SARS CoV-2 diagnostic tests in different settings we evaluated the performance of Ag-RDT-based and a cell-culture-based SARS-CoV-2 assay in comparison to rRT-PCR. Study design: A total of 61 Nasopharyngeal-Swabs tested positive by cobas® SARS-CoV-2 rRT-PCR were in parallel evaluated with the Roche Ag-RDT and a cell culture-based assay to detect SARS-CoV-2. Results: SARS-CoV-2 was successfully isolated in 51/61 samples corresponding to 83.6%, which was 97.3% or 96.2% when considering samples with E-gene Ct-value <25 and <28, respectively. In comparison, the Ag-RDT showed an overall sensitivity of 85.2%, that increased to 100% and 96.2% using an E-gene Ct-value cut-off of <25 and <28, respectively. There was an overall good agreement between the commercial Ag-RDT and our in-house cell culture-based SARS-CoV-2 detection assay. However, SARS-CoV-2 could be isolated from two samples that tested negative by Ag-RDT. Conclusions: Our results support the use of the Roche Ag-RDT to detect SARS-CoV-2 exposure in large scale populations. However, it is recommended to use rRT-PCR, potentially in conjunction with cell culture-based SARS-CoV-2 assay, to support clinicians in making decisions regarding fragile patient groups. respectively. In comparison, the Ag-RDT showed an overall sensitivity of 85.2%, that 27 increased to 100% and 96.2% using an E-gene Ct-value cut-off of <25 and <28, 28 respectively. There was an overall good agreement between the commercial Ag-RDT and 29 our in-house cell culture-based SARS-CoV-2 detection assay. However, SARS-CoV-2 could 30 be isolated from two samples that tested negative by Ag- RDT. 31 Conclusions: Our results support the use of the Roche Ag-RDT to detect SARS-CoV-2 32 exposure in large scale populations. However, it is recommended to use rRT-PCR, 33 potentially in conjunction with cell culture-based SARS-CoV-2 assay, to support clinicians in 34 making decisions regarding fragile patient groups. The current reference method for SARS-CoV-2 detection relies on real-time reverse 51 transcriptase polymerase chain reaction (rRT-PCR) [ (Table 1 and Suppl Table 181 1). In contrast, five samples showed a discrepancy in the outcome between both assays. other studies, which all demonstrate that the success rate of SARS-CoV-2 isolation is related 218 to the viral load/Ct-value within a clinical specimen [19] [20] [21] [22] [24] [25] [26] [27] [28] [29] . Because cell culture-219 based virus isolation methods are well suited to discern between non-and infectious virus it 220 has been suggested that a certain rRT-PCR Ct-value cut-off potentially could be used as a 221 surrogate to define when a patient with COVID19 can be released from isolation [20, 25, 30] . 222 However, due to the reported differential Ct-value cut-offs (ranging from 24 to 34) between 223 infectious and non-infectious SARS-CoV-2 [19, 20, 22, 24] it will be necessary to standardize 224 and potentially improve the detection sensitivity of SARS-CoV-2 cell culture-based 225 diagnostic assays prior to implementing such cut-offs in practice. 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