Lumipulse G SARS-CoV-2 Ag assay evaluation using clinical samples from different testing groups.

Area of Science:

• Clinical diagnostics
• Virology
• Immunology

Background:

• Antigen detection assays for SARS-CoV-2, like the Lumipulse G assay, may exhibit variable performance compared to RT-PCR.
• Performance can be influenced by specific testing scenarios and sample characteristics.

Purpose of the Study:

• To evaluate the performance of the Lumipulse G SARS-CoV-2 Ag assay.
• To compare its sensitivity and specificity against RT-PCR across different testing groups and viral loads.

Main Methods:

• Tested 594 nasopharyngeal swab samples using both RT-PCR and the Lumipulse G assay.
• Categorized samples based on RT-PCR cycle threshold (Ct) values (≤40 for COVID-19 positive, >40 for negative).
• Assigned RT-PCR positive samples into diagnostic, screening, or monitoring groups.

Main Results:

• Lumipulse assay demonstrated a positive percent agreement (PPA) of 79.9% and negative percent agreement of 99.3% compared to RT-PCR.
• PPA was 100% for samples with very low Ct values (<25) and decreased with higher Ct values.
• Testing for subgenomic RNA revealed lower PPA for Lumipulse, particularly in samples with higher Ct values.

Conclusions:

• The Lumipulse assay is highly sensitive in samples with low RT-PCR Ct values (high viral load).
• Performance may vary in scenarios with lower viral loads or specific testing purposes.
• Consideration of repeated testing is advised to mitigate the impact of potential false-negative results.