Detection of SARS-CoV-2 in Saliva using the BinaxNOW™ COVID-19 Antigen Self Test

Abstract We conducted a pilot study to determine if the BinaxNOW rapid antigen test can detect SARS-CoV-2 antigen in saliva, in place of the specified nasal (Nares) swab sample. A nasal swab may not provide an optimal sample for detecting Omicron, now the predominant variant, because Omicron sheds a greater viral load into saliva than into the nasal passages. Saliva was obtained from non-infected donors, spiked with varying concentrations of heat-denatured SARS-CoV-2 virus, and tested using the BinaxNOW kit following the manufacturer’s instructions. The BinaxNOW test detected COVID-19 in saliva samples with a Limit of Detection (LOD) of 178 TCID50/mL saliva, which was the lowest concentration tested. This detection sensitivity is comparable to the LOD reported by the manufacturer for BinaxNOW (140.6 TCID50/mL) using nasal samples. This result shows that the BinaxNOW test can detect SARS-CoV-2 in saliva with a detection power comparable to that obtained using nasal swab samples.