Field evaluations of four SARS-CoV-2 rapid antigen tests during SARS-CoV-2 Delta variant wave in South Africa

Abstract Background: Rapid antigen tests detecting SARS-CoV-2 are being increasingly used across the globe and were shown to be a useful tool in managing the COVID-19 pandemic. The purpose of this prospective study was to characterise the performance of four SARS-CoV-2 rapid antigen tests in a South African setting. Methods: Rapid antigen test evaluations were performed through drive-through testing centres in Durban, South Africa from July-December 2021. Two evaluation studies were performed: nasal Panbio COVID-19 Ag Rapid Test Device (Abbott) was evaluated in parallel with the nasopharyngeal Espline SARS-CoV-2 Ag test (Fujirebio, nasopharyngeal); followed by the evaluation of nasal RightSign COVID-19 Antigen Rapid test Cassette (Hangzhou Biotest Biotech) in parallel with the nasopharyngeal STANDARD Q COVID-19 Ag test (SD Biosensor). The Abbott RealTime SARS-CoV-2 assay was used as a reference test. Results: Evaluation of Panbio and Espline Ag tests was performed on 494 samples (31% positivity) while the evaluation of Standard Q and RightTest Ag tests was performed on 539 samples (13.17 % positivity). The overall sensitivity for all four tests ranged between 60-72% with excellent specificity values (>98%). Sensitivity increased to >80% in all tests in samples with Ct value <20. All four tests performed best in samples from patients presenting within the first week of symptom onset. Conclusions: All four evaluated tests detected a majority of the cases within the first week of symptom onset with high viral load and could be a valuable diagnostic tool for controlling the spread of SARS-CoV-2.