Impact of Omicron variant sublineage BA.2.75 on the OnSite COVID-19 Ag Rapid Test: the applicability of rapid antigen test with universal transport media

Abstract

Background

Rapid antigen testing (RAT) is one of the most powerful tools for SARS-CoV-2 detection. The OnSite COVID-19 Ag Rapid Test is an antigen-based, point-of-care test approved by the WHO for Emergency Use Listing. The Nucleocapsid (N) gene mutations found in the emerging Omicron sublineages lead to the question of RAT performance.

Objective

To ensure the diagnostic performance of the study RAT during rapidly mutated Omicron variants.

Results

We independently evaluated the performance of this assay in 1098 archived samples collected in Thailand during October 2022–February 2023, which were 798 and 300 COVID-19 real-time RT-PCR positive and negative, respectively. The assay performed with 100% sensitivity and 100% specificity using a cycle threshold (Ct) of <20 for the RT-PCR. The sensitivity decreased to 88% when using Ct <30. Most of the SARS-CoV-2 found were Omicron BA.2 (99%), harboring six known N mutations (P13L, E31del, S33del, R203K, G204R and S413R). Eight samples containing hybrid variants (XBB.1*, XBB.2 and XBJ) were detected by the study RAT. This RAT detects all Omicron sublineages known to be circulating in Thailand.

Conclusions

These results confirmed the good performance of the study RAT for detecting Omicron variants and its appropriateness for individual diagnosis and for genomic surveillance.

Keywords:

• SARS-CoV-2
• rapid antigen test
• Omicron variant
• diagnostic performance

Acknowledgements

We thank the World Health Organization (WHO) for supporting the scientific reagents and the OnSite^® COVID-19 Ag Test. We also thank all staff of the Division of Respiratory Viral Infections, Thai National Institute of Health, the Ministry of Public Health for the study management.

Ethical approval

This research study was approved by the Ethical Committee of the Institute for the Development of Human Research Protection, Department of Medical Sciences, MoPH (COA no. IHRP2021093).

Author contributions

PO: study design, data analysis and study management. PN: study design, data analysis and manuscript writing. CP: data analysis. KB, SP and NT: specimen processing, laboratory experiment and bioinformatic analysis. AR, BU and SS: study design and discussion.

Disclosure statement

The authors declare that they have no competing interest.

Data availability statement

The data analyzed in the current study are available upon request to the author.

Additional information

Funding

The research project was supported by the World Health Organization under the theme of ‘Public Health Surveillance for COVID-19 in Thailand’.