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 [preprint]
Program in Digital Medicine, Department of Medicine; Department of Population and Quantitative Health Sciences; Division of Clinical Informatics, Department of Medicine; Department of Emergency Medicine; Department of Microbiology and Physiological Systems; Department of Pediatrics; UMass Center for Clinical and Translational Science; Division of Infectious Diseases and Immunology, Program in Molecular Medicine; Division of Cardiovascular Medicine, Department of Medicine
Epidemiology | Immunology and Infectious Disease | Infectious Disease | Microbiology | Virus Diseases
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 sensitivity, defined as proportion of participants with Ag-RDT+ results in relation to their first RT-PCR+ result, for different duration of testing with rapid Ag-RDT. 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 analysis. 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 84 (54.9%) tested Ag-RDT+ within 48 hours as first RT-PCR+. The differences in sensitivity 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]; and 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 (48-hour sensitivity: Delta 79.3% [60.3-92.1] vs. Omicron: 89.5% [78.5-96.0]). Conversely, the 38 participants who had an isolated RT-PCR+ remained consistently negative on Ag-RDT, regardless of the variant.
Conclusions The performance of Ag-RDT is not inferior among individuals infected with the SARS-CoV-2 Omicron variant as compared to the Delta variant. The improvement in sensitivity of Ag-RDT noted 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.
Infectious Diseases, rapid antigen tests, SARS-CoV-2, UMCCTS funding
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DOI of Published Version
medRxiv 2022.02.27.22271090; doi: https://doi.org/10.1101/2022.02.27.22271090. Link to preprint on medRxiv.
Soni A, Herbert C, Filippaios A, Broach JP, Colubri A, Fahey N, Woods K, Nanavati J, Wright C, Orwig T, Gilliam K, Lin H, O'Connor L, Pretz C, Ayturk MD, Orvek EA, Flahive JM, Lazar P, Shi Q, Gibson LL, Stamegna P, Hafer NS, Luzuriaga K, Barton BA, McManus DD, RADx Clinical Studies Core team and Test Us At Home Investigators. (2022). 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 [preprint]. UMass Chan Medical School Faculty Publications. https://doi.org/10.1101/2022.02.27.22271090. Retrieved from https://escholarship.umassmed.edu/faculty_pubs/2209