Comparison of performance of LIAISON SARS-CoV-2 antigen assay with RT-PCR during the Omicron wave

Due to the newly emerging Omicron variant, there is a need to re-evaluate the performance of automated antigen tests. Our study aim was to evaluate the performance of the automated Liaison SARS-CoV-2 antigen assay against reverse transcriptase polymerase chain reaction (RT-PCR) in samples with Omicron variant.A prospective study was performed on 373 combined oro-nasopharyngeal samples (NPS) randomly collected from symptomatic patients. NPS were tested with Liaison SARS-CoV-2 Ag test (DiaSorin, Italy) and DS Coronex COVID-19 Multiplex RT-PCR Diagnosis Kit (DS BioTechnology, Ankara, Turkey).Of 373 samples, 124 (33.2%) were found to be RT-PCR positive and 249 (66.8%) RT-PCR negative. Taking RT-PCR as a reference, the sensitivity and specificity of the Liaison SARS-CoV-2 Ag assay were found as 84.6% (95%CI 77.3%-90%) and 100% (95%CI 98.5%-100%), respectively. For samples with a cycle threshold (Ct) value <25 (high viral load), the sensitivity increased to 100%. When antigen concentration and Ct values were compared, a strong negative correlation between antigen and Ct values was determined (P < 0.001).The Liaison antigen test met the performance criteria recommended by the WHO for samples with the Omicron variant. In addition, it showed excellent sensitivity and specificity in patients with high viral load. Therefore, Liaison antigen test can be a reliable and useful alternative in the diagnosis of SARS-CoV-2 infection, particularly in resource-constrained laboratories.