Wide Real-Life Data Support Reduced Sensitivity of Antigen Tests for Omicron SARS-CoV-2 Infections

Area of Science:

• Virology
• Infectious Diseases
• Diagnostic Technologies

Background:

• Continuous emergence of SARS-CoV-2 variants of concern (VOCs) necessitates ongoing monitoring of diagnostic test performance.
• Antigen diagnostic tests (ADTs) are crucial for rapid SARS-CoV-2 detection, but their sensitivity may be impacted by viral mutations.

Purpose of the Study:

• To evaluate the change in accuracy of ADTs during the transition from SARS-CoV-2 Delta to Omicron variants.
• To investigate potential impacts of N protein mutations on ADT sensitivity.
• To determine the optimal sampling site for diagnosing Omicron infections.

Main Methods:

• Retrospective analysis of 5175 subjects with paired ADT and RT-PCR tests from October 2021 to July 2022.
• Prospective analysis of nasal and oral swabs from 61 patients during the Omicron wave using RT-PCR.
• Next-Generation Sequencing to analyze SARS-CoV-2 sublineages.

Main Results:

• Overall ADT sensitivity decreased significantly from 63% during the Delta period to 33% during the Omicron period (p < 0.001).
• No significant decrease in viral load at the RNA level was observed.
• Nasal swabs showed a significantly higher viral load compared to oral swabs during the Omicron wave.

Conclusions:

• The reduced sensitivity of ADTs against Omicron variants poses a challenge for accurate diagnosis.
• Testing strategies must adapt to the evolving SARS-CoV-2 landscape to maintain diagnostic accuracy.
• Nasal sampling is recommended for improved detection of Omicron infections.