Rapid antigen tests are most effective when used multiple times to detect SARS-CoV-2 infection
1. In this prospective cohort study, rapid coronavirus disease 2019 (COVID-19) antigen tests had optimal performance when asymptomatic participants were tested three times at 48-hour intervals.
2. Additionally, rapid antigen tests had an optimal performance for symptomatic participants when they tested two times at 48-hour intervals.
Evidence Rating Level: 1 (Excellent)
Study Rundown: At-home rapid antigen tests (Ag-RDTs) for COVID-19 offer a fast and convenient testing option. Although, reports on Ag-RDT performance have demonstrated heterogeneous results with sensitivities ranging from 35.8% to 71% in cross-sectional screening evaluations for asymptomatic persons. Accordingly, there is a gap in knowledge as to understanding the performance of Ag-RDTs when serial testing is performed among asymptomatic persons. Overall, this study found that the performance of Ag-RDTs was optimized when asymptomatic and symptomatic participants with COVID-19 used the tests three and two times, respectively, at 48-hour intervals. This study was limited by Ag-RDTs being self-performed and specimens being self-collected for RT-PCR. Nevertheless, these study’s findings are significant, as they demonstrate that the performance of serial testing using Ag-RDTs for detection of SARS-CoV-2 among symptomatic and asymptomatic persons within the first week of infection is optimal at 48-hour intervals.
Click to read the study in AIM
Relevant Reading: Comparison of Rapid Antigen Tests’ Performance Between Delta and Omicron Variants of SARS-CoV-2
In-Depth [prospective cohort study]: This prospective cohort study was conducted between October 2021 and January 2022. Persons who had not had a SARS-CoV-2 infection in the prior three months, had been without any symptoms in the 14 days before enrollment, and were able to drop off prepaid envelopes with nasal swab samples at their local FedEx drop-off location were eligible for the study. Patients who were not able to self-enroll were excluded from the study. The primary outcome measured was the results of Ag-RDTs based on self-reporting (Quidel QuickVue At-Home OTC COVID-19 Test and BinaxNOW COVID-19 Antigen Self Test) or an automatic reader (BD Veritor At-Home COVID-19 Test), according to the instructions for use. Outcomes in the primary analysis were assessed via sensitivity analysis using a bootstrapping technique. Based on the primary analysis, serial testing with Ag-RDTs twice 48 hours apart resulted in an aggregated sensitivity of 93.4% (95% CI, 90.4% to 95.9%) among symptomatic participants on different days past index polymerase chain reaction positivity (DPIPPs) 0 to 6. When singleton positive results were excluded, the aggregated sensitivity on DPIPPs 0 to 6 for two-time serial testing among asymptomatic participants was lower at 62.7% (CI, 57.0% to 70.5%), but it improved to 79.0% (CI, 70.1% to 87.4%) with testing three times at 48-hour intervals. In summary, this study demonstrates that for asymptomatic persons, the performance of Ag-RDTs is optimized when persons are tested three times at 48-hour intervals compared to two times in those who are symptomatic.
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