Reduced Relative Sensitivity of the Elecsys SARS-CoV-2 Antigen Assay in Saliva Compared to Nasopharyngeal Swabs

Early identification and isolation of SARS-CoV-2-infected individuals is central to contain the COVID-19 pandemic. Nasopharyngeal swabs (NPS) serve as a specimen for detection by RT-PCR rapid antigen screening tests. Saliva has been confirmed reliable alternative shown be valuable diagnosing children in repetitive mass testing due its non-invasive collection. Combining advantages saliva with those tests would highly attractive further increase test capacities. Here, we evaluated performance Elecsys SARS-CoV-2 Antigen assay (Roche) RT-PCR-positive paired NPS samples (N = 87) unpaired 100) infection (Roche cobas IVD test). We observed high positive percent agreement (PPA) NPS, reaching 87.2% across entire cohort, whereas overall PPA was insufficient (40.2%). At Ct values ? 28, were 100% 91.2% saliva, respectively. lower viral loads, sensitivity loss striking. 35, remained satisfactory (91.5%), dropped 46.6%. In conclusion, cannot recommended Anti-SARS-CoV-2 assay. As successfully used broadly combination testing, it critical create awareness that suitability translated implementation assays without thorough evaluation each individual system.