key: cord-0429840-oye10k73
authors: Drain, P. K.; Bemer, M.; Morton, J. F.; Dalmat, R.; Abdille, H.; Thomas, K.; Uppal, T.; Hau, D.; Green, H. R.; Hollingworth, M.; Aucoin, D. P.; Verma, S. C.
title: Accuracy of Rapid Antigen Testing across SARS-CoV-2 Variants
date: 2022-03-23
journal: nan
DOI: 10.1101/2022.03.21.22272279
sha: d38eee2450db7f52b06f415371c2ac19c595d875
doc_id: 429840
cord_uid: oye10k73

Variants of SARS-CoV-2 have mutations in the viral genome that may alter the accuracy of rapid diagnostic tests. We conducted analytical and clinical accuracy studies of two FDA-approved rapid antigen tests, SCoV-2 Ag Detect Rapid Test (InBios International, Seattle) and BinaxNOW COVID-19 Ag CARD; (Abbott Laboratories, Chicago), using three using replication-competent variants or strains, including Omicron (B.1.1.529/BA.1), Delta (B.1.617.2), and a wild-type of SARS-CoV-2 (USA-WA1/2020). Overall, we found non-significant differences in the analytical limit of detection or clinical diagnostic accuracy of rapid antigen testing across SARS-CoV-2 variants. This study provides analytical and clinical performance data to demonstrate the preserved accuracy of rapid antigen testing across SARS-CoV-2 variants among symptomatic adults.

Variants of SARS-CoV-2 have mutations in the viral genome that may alter the accuracy of rapid diagnostic tests. 1 Molecular tests can be affected by single point mutations, whereas antigen tests may require multiple mutations to change the confirmation of viral protein epitopes.

The Omicron variant has numerous mutations in the spike and nucleocapsid proteins, 2 which has raised concerns about the analytical and clinical accuracy of rapid antigen testing. 3 We conducted an analytical accuracy study of two FDA-approved rapid antigen tests-SCoV-2

Ag Detect™ Rapid Test (InBios International, Seattle) and BinaxNOW™ COVID-19 Ag CARD; (Abbott Laboratories, Chicago)-using three using replication-competent variants or and USA-WA1/2020 strain (GenBank: MN985325.1) of SARS-CoV-2, which have known TCID 50 values of 1.1 x10 6 and 1.6 x10 6 , respectively, for comparative analytical testing.

Performance and the analytical limit of detection for Omicron detection were measured by spiking negative clinical nasal swab matrices with replication-competent virus to establish three stock viral concentrations of 5.0 x10 4 , 1.25 x10 4 , and 3.12 x10 3 TCID 50 /mL. From stock concentrations, we transferred 20 µL of sample onto nasal swabs to generate high, medium, and low viral concentrations of 1,000, 250, 62.5 TCID 50 per swab, respectively. We tested the viral . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted March 23, 2022. ; dilutions across variants in triplicate for both the SCoV-2 Ag Detect™ Rapid Test ( Figure S1) and BinaxNOW™ COVID-19 Ag CARD ( Figure S2 ). Based on the visual signal intensity, the limit of detection for these rapid nucleocapsid antigen tests was approximately 62.5 TCID 50 , which is equivalent to 51 PFUs ( Figure S3 ).

To complement the analytical accuracy study of the SCoV-2 Ag Detect™ Rapid Test, we further conducted a clinical diagnostic accuracy study among 802 participants at multiple testing locations in King County, Washington from February 2021-January 2022, during three distinct phases of SARS-CoV-2 infections (pre-Delta, Delta, Omicron) (Table S1 ). Participants were 18 years old reporting onset of Covid-19-like symptoms within the prior five days. We collected two anterior nasal swabs-one for on-site testing by the SCoV-2 Ag Detect™ Rapid Test and one for reverse transcriptase polymerase chain reaction (rt-PCR) testing. The study received ethical approval from the University of Washington (STUDY00009981), and participants provided verbal informed consent.

Overall, we found non-significant differences in the analytical limit of detection or clinical diagnostic accuracy of rapid antigen testing across SARS-CoV-2 variants ( Table 1 ). The positive percent agreement ranged from 81-91%, with improved sensitivity for swabs with a lower cycle threshold, which correlates to a higher viral load (Table S2) . Visual signals were positively associated with viral concentration and had more variation at low concentrations ( Figure S1 and S2). We found no real differences for clinical test performance by vaccination status or days since symptom onset (Table S2 ). The negative percent agreement was high across study periods.

This study provides analytical and clinical performance data to demonstrate the preserved accuracy of rapid antigen testing across SARS-CoV-2 variants among symptomatic adults. Other studies have similarly demonstrated good analytical sensitivity for rapid antigen tests to detect Omicron, 5,6 and with similar limits of analytical detection between the Omicron variant and USA-WA1/2020 strain. 7 A field study has shown the BinaxNOW™ COVID-19 Ag CARD to have good clinical accuracy for Omicron. 8 Our study has demonstrated both the analytical and clinical accuracy of rapid antigen testing across several variants of concern, including Omicron and Delta.

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 23, 2022. ; https://doi.org/10.1101/2022.03.21.22272279 doi: medRxiv preprint A study strength was detecting circulating variants representative of the community prevalence over a 12-month period, and additional clinical and analytical comparative studies may still be warranted for other rapid antigen tests. Since rapid antigen tests may correlate with recovery of replication-competent SARS-CoV-2 9 and appear to retain accuracy across variants, ongoing home-based rapid antigen testing programs may be an important intervention to reduce global SARS-CoV-2 transmission.

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 23, 2022. ; https://doi.org/10.1101/2022.03.21.22272279 doi: medRxiv preprint

The study was supported by InBios International Inc., which had no role in the data analyses, interpretation, or reporting of these results. Dr. Drain reports receiving grant support, paid to his institution, from the National Institutes of Health, the Centers for Disease Control and . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) .

It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 23, 2022. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 23, 2022. ; 

Rapid diagnostic testing for SARS-CoV-2

Classification of Omicron (B.1.1.529): SARS-CoV-2 variant of concern

SARS-CoV-2 viral mutations: Impact on COVID-19 tests

Quantification of SARS-CoV-2 neutralizing antibody by wild-type plaque reduction neutralization, microneutralization and pseudotyped virus neutralization assays

Assessment of the analytical sensitivity of ten lateral flow devices against the SARS-CoV-2 omicron variant

Sensitivity of SARS-CoV-2 antigen-detecting rapid tests for Omicron variant

Limit of Detection for Rapid Antigen Testing of the SARS-CoV-2 Omicron Variant

Direct comparison of SARS-CoV-2 nasal RT-PCR and rapid antigen test (BinaxNOW™) at a community testing site during an Omicron surge

Relationship of SARS-CoV-2 Antigen and Reverse Transcription PCR Positivity for Viral Cultures