Positive Concordance between Commercially Available SARS-CoV-2 Rapid Antigen Test and RT-PCR during the Omicron Wave in Thailand

Abstract

Background: Rapid SARS-CoV-2 antigen tests are widely used throughout the world. False positive antigen tests have been reported. Objective: To evaluate the positive percentage concordance (PPC) between a rapid antigen test and the nucleic acid amplification testing (NAAT). Materials and Methods: The present study was a retrospective laboratory-based study on rapid antigen test-positive nasopharyngeal or throat swabs sent for confirmation by real-time reverse transcriptase polymerase chain reaction (rRT-PCR) between January 1 and April 8, 2022. The primary outcome was a PPC between antigen-positive samples and PCR-positive samples. Results: Of the 22,808 samples received, there were 3,656 or 16.04% of the samples with documented positive rapid antigen tests sent for confirmation by rRT-PCR. Overall, PPC was 92.67%, 95% CI 91.82 to 93.51. A higher PPC was found during the BA.2-dominant Omicron variant period at 96.08% (95% CI 95.2 to 96.95). Conclusion: The PPC between the rapid antigen test used and rRT-PCR was very high, especially during the BA.2-dominant period. Keywords: Rapid antigen test; Omicron; rT-PCR; Positive percentage concordance