Accuracy of 2 Rapid Antigen Tests During 3 Phases of SARS-CoV-2 Variants

IMPORTANCE: Variants of SARS-CoV-2 have sequence variations in the viral genome that may alter the accuracy of rapid diagnostic tests. OBJECTIVE: To assess the analytical and clinical accuracy of 2 rapid diagnostic tests for detecting SARS-CoV-2 during 3 phases of variants. DESIGN, SETTING, AND PARTICIPANTS: This diagnostic study included participants aged 18 years or older who reported onset of COVID-19–like symptoms within the prior 5 days and were tested at multiple COVID-19 testing locations in King County, Washington, from February 17, 2021, to January 11, 2022, during 3 distinct phases of SARS-CoV-2 infection (pre-Delta, Delta, and Omicron). INTERVENTIONS: Two anterior nasal swab specimens were collected from each participant—1 for onsite testing by the SCoV-2 Ag Detect Rapid Self-Test and 1 for reverse transcriptase–polymerase chain reaction (RT-PCR) testing. MAIN OUTCOMES AND MEASURES: The analytical limit of detection of the 2 rapid diagnostic tests (SCoV-2 Ag Detect Rapid Self-Test and BinaxNOW COVID-19 Ag Card) was assessed using Omicron (B.1.1.529/BA.1), Delta (B.1.617.2), and a wild-type (USA-WA1/2020) variant. Diagnostic sensitivity and specificity of clinical testing for the rapid antigen tests were compared with that of RT-PCR testing. RESULTS: A total of 802 participants were enrolled (mean [SD] age, 37.3 [13.3] years; 467 [58.2%] female), 424 (52.9%) of whom had not received COVID-19 vaccination and presented a median of 2 days (IQR, 1-3 days) from symptom onset. Overall, no significant differences were found in the analytical limit of detection or clinical diagnostic accuracy of rapid antigen testing across SARS-CoV-2 variants. The estimated limit of detection for both rapid nucleocapsid antigen tests was at or below a 50% tissue culture infectious dose of 62.5, and the positive percent agreement of the SCoV-2 Ag Detect Rapid Self-Test ranged from 81.2% (95% CI, 69.5%-89.9%) to 90.7% (95% CI, 77.9%-97.4%) across the 3 phases of variants. The diagnostic sensitivity increased for nasal swabs with a lower cycle threshold by RT-PCR, which correlates with a higher viral load. CONCLUSIONS AND RELEVANCE: In this diagnostic study, analytical and clinical performance data demonstrated accuracy of 2 rapid antigen tests among adults with COVID-19 symptoms across 3 phases of SARS-CoV-2 variants. The findings suggest that home-based rapid antigen testing programs may be an important intervention to reduce global SARS-CoV-2 transmission.