1. Rapid antigen tests had similar sensitivity in detecting omicron and delta variants of coronavirus disease 2019 (COVID-19).
2. Rapid antigen test performance was most effective when reverse transcription polymerase chain reaction (RT-PCR) results were positive for more than 48 hours.
Evidence rating level: 1 (Excellent)
Study Summary: Rapid antigen tests to detect COVID-19 have been shown to be easy to use, accessible, and cost-effective to help identify infections to inform isolation recommendations and prevent transmission. However, rapid antigen tests have lower sensitivity than RT-PCR tests for detecting SARS-CoV-2. In particular, the sensitivity can be improved by serial testing. There is a critical knowledge gap in understanding the performance of rapid antigen tests for detecting the omicron variant, as early reports have said that they have lower sensitivity for the omicron variant than for other variants. Overall, this study found that the performance of the nasal swab rapid antigen test was similar between the omicron and delta variants. This study was limited by having a 48-hour testing frequency, which does not allow finer temporal resolution of test performance analysis, and rapid antigen test results were based on self-reports. Nonetheless, these findings are significant as they demonstrate that the performance of rapid antigen tests in people infected with the omicron variant is not inferior to that of people infected with the delta variant.
in deep [prospective cohort study]: This secondary analysis of a prospective cohort study studied participants who performed rapid antigen tests and underwent RT-PCR testing every 48 hours for 15 days. People who enrolled between October 2021 and February 2022, who resided in any state except Hawaii, Alaska, or Arizona, and who had access to a smartphone, were eligible for the study. Patients with symptoms of COVID-19 in the 14 days prior to enrollment or with a self-reported positive COVID-19 test result in the previous three months were excluded from the study. The primary outcome measured was the sensitivity of rapid antigen tests on the same day as the first positive RT-PCR result and 48 hours after the first positive RT-PCR result. The results of the primary analysis were evaluated using Fisher’s exact test and differences in sensitivity using Taylor’s linearization. Based on the primary analysis, differences in sensitivity between variants were not statistically significant in same-day testing. [(Delta: 15.5%; 95% Confidence Interval [CI]6.2% to 24.8%) vs (Omicron: 22.1%; 95% CI, 15.5% to 28.8%)]or at 48 hours [(Delta: 44.8%; 95% CI, 32.0% to 57.6%) vs. (Omicron: 49.7%; 95% CI, 41.6% to 57.6%)]. In addition, rapid antigen sensitivity did not differ significantly between delta- and omicron-infected participants in participants who had positive RT-PCR results for 48 hours. [(Delta: 81.5%; 95% CI, 66.8% to 96.1%) vs. (Omicron: 78.0%; 95% CI, 69.1% to 87.0%)]. Overall, this study demonstrates that rapid antigen tests provided similar sensitivities and efficacy in detecting omicron and delta variants of SARS-CoV-2.
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