Comparison of Rapid Antigen Tests’ Performance between Delta (B.1.61.7; AY.X) and Omicron (B.1.1.529; BA1) Variants of SARS-CoV-2: Secondary Analysis from a Serial Home Self-Testing Study

Abstract

Background: There is a need to understand the performance of rapid antigen tests (Ag-RDT) for detection of the Delta (B.1.61.7; AY.X) and Omicron (B.1.1.529; BA1) SARS-CoV-2 variants. Methods: Participants without any symptoms were enrolled from October 18, 2021 to January 24, 2022 and performed Ag-RDT and RT-PCR tests every 48 hours for 15 days. This study represents a non-pre-specified analysis in which we sought to determine if sensitivity of Ag-RDT differed in participants with Delta compared to Omicron variant. Participants who were positive on RT-PCR on the first day of the testing period were excluded. Delta and Omicron variants were defined based on sequencing and date of first RT-PCR positive result (RT-PCR+). Comparison of Ag-RDT performance between the variants was based on proportion of participants with Ag-RDT+ results in relation to their first RT-PCR+ result. Subsample analysis was performed based on the result of participants′ second RT-PCR test within 48 hours of the first RT-PCR+ test. Results: From the 7,349 participants enrolled in the parent study, 5,506 met the eligibility criteria for this study. A total of 153 participants were RT-PCR+ (61 Delta, 92 Omicron); among this group, 36 (23.5%) tested Ag-RDT+ on the same day and 36 (23.5%) tested Ag-RDT+ within 48 hours as first RT-PCR+. The differences between variants were not statistically significant (same-day: Delta 16.4% [95% CI: 8.2-28.1] vs Omicron 28.2% [95% CI: 19.4-38.6; 48-hours: Delta 45.9% [33.1-59.2] vs. Omicron 60.9% [50.1-70.9]). This trend continued among the 86 participants who had consecutive RT-PCR+ result (Delta: 79.3% [60.3-92.1] vs. Omicron: 89.5% [78.5-96.0]). Conversely, the 38 participants who had an isolated positive RT-PCR remained consistently negative on Ag-RDT, regardless of the variant. Conclusions: The performance of Ag-RDT is not inferior among Omicron variant in comparison to the Delta variant. The improvement in sensitivity of Ag-RDT with serial testing is consistent between Delta and Omicron variant. Performance of Ag-RDT varies based on duration of RT-PCR+ results and more studies are needed to understand the clinical and public health significance of individuals who are RT-PCR+ for less than 48 hours.

Daily Rapid Antigen Testing in a University Setting to Inform COVID-19 Isolation Duration Policy

“…9–11 To investigate concerns that RATs may have inferior performance for Omicron versus Delta infections, a study compared same-day positivity between the variants, finding similar sensitivity of RAT and PCR tests. 12 Lastly, RATs have the advantage of relative affordability, fast turnaround time, and at-home self-administration compared to PCR, making them the only viable exit test option for much of the population. 13,14…”

“…[9][10][11] To investigate concerns that RATs may have inferior performance for Omicron versus Delta infections, a study compared same-day positivity between the variants, finding similar sensitivity of RAT and PCR tests. 12 Lastly, RATs have the advantage of relative affordability, fast turnaround time, and at-home self-administration compared to PCR, making them the only viable exit test option for much of the population. 13,14 To address the evidence gaps regarding optimal isolation durations and how SARS-CoV-2-positive persons can best utilize exit RATs when resources are limited, we evaluated daily RAT data from 324 persons in a university-managed isolation program who initially tested positive for SARS-CoV-2 between January 1 and February 11, 2022.…”

Comparison of BinaxNOW TM and SARS-CoV-2 qRT-PCR detection of the Omicron Variant from Matched Anterior Nares Swabs

“…This result provided important information regarding our ability to implement BinaxNOW TM , antigen-based testing, as a surrogate for qRT-PCR testing. A cutoff value of 24 for qRT-PCR is below the average C T value reported for both delta and omicron variants (5,6,8,9,12,13), suggesting that RDT testing alone would be insufficient to maintain control of spread in our community (Supplementary Table 3). Thus, the conclusion of our qualification study was that it is not possible to use the BinaxNOW TM test alone to replace qRT-PCR in our testing sites for ruling-out positive individuals.…”

“…These studies suggested that there was analytical strength in the RDT, but also suggested a limited range of viral loads in which the assays consistently returned positive results from PCR positive samples. Two additional studies look at a broader range of SARS-CoV-2 RDT tests include a 15-day study of individuals with no symptoms comparing delta and omicron on 3 RDT tests (13) and a study testing previously PCR tested frozen samples on 5 different RDT tests (14).…”

Association of Mass Distribution of Rapid Antigen Tests and SARS-CoV-2 Prevalence: Results from NIH-CDC funded Say Yes! Covid Test program in Michigan

“…These findings, taken together with recent reports that rapid antigen tests’ performance remain consistent across variants, underscore the continued utility of rapid antigen tests. 9 With emerging reports of the BA.2 variant causing a surge in cases across the globe and in the United States, these findings hold particular importance for the public health of the country.…”