Comparison of the Quantitative DiaSorin Liaison Antigen Test to Reverse Transcription-PCR for the Diagnosis of COVID-19 in Symptomatic and Asymptomatic Outpatients

Abstract

Background:We evaluated the quantitative DiaSorin Liaison SARS-CoV-2 antigen test in symptomatic and asymptomatic individuals consulting their general practioner (GP) during a period of stable intense virus circulation (213/100,000 habitants per day). Methods:Left-over RT-PCR positive (n=204) and negative (n=210) nasopharyngeal samples were randomly selected among fresh routine samples collected from patients consulting their GP. Samples were tested on Liaison XL according to the manufacturer’s instructions. Equivocal results were considered positive. Results:Overall sensitivity and specificity of the Liaison antigen test compared to RT-PCR were 67.7% [95% confidence interval (CI): 60.9%-73.7%] and 100% [CI: 97.8%-100%]. Sensitivity in samples with a viral load ≥105, ≥104 and ≥103 copies/mL was 100% [CI: 96.3%-100.0%], 96.5% [CI: 91.8%-98.7%] and 87.4% [CI: 81.3%-91.5%], respectively. All samples ≤103 copies/mL were antigen negative. The ratio of antigen concentration to viral load in samples ≥103 copies/mL was comparable in symptomatic and asymptomatic individuals (p=0.58). The proportion of RT-PCR positive participants with a high viral load (≥105 copies/mL) was not significantly higher in symptomatic than in asymptomatic participants (63.9% [CI: 54.9%-72.0%] vs. 51.9% [CI: 41.1%-62.6%], p=0.11), but the proportion of participants with a low viral load (<103 copies/mL) was significantly higher in asymptomatic than in symptomatic RT-PCR positive participants (35.4% [CI: 25.8%-46.4%] vs. 14.3% [CI: 9.0%-21.8%], p<0.01). Conclusions:Sensitivity and specificity in samples with a viral load ≥104 copies/mL was 96.5% and 100%. The correlation of antigen concentration with viral load was comparable in symptomatic and asymptomatic individuals.

Evaluation and modelling of the performance of an automated SARS-CoV-2 antigen assay according to sample type, target population and epidemic trends

“…As expected, saliva yielded less good performance and should be restricted to settings with limited access to sampling disposable or patients presenting contra-indication for naso-pharyngeal sampling. Comparable results were previously obtained on saliva and on other instruments [6–8].…”

Comparison of four commercial, automated antigen tests to detect SARS-CoV-2 variants of concern

“…between 91 and 100% [5][6][7][8][9][10][11][12][13][14][15][16]. While assay specificities were frequently found to be relatively high [5][6][7][8][9][10][11][12][13][14][15][16], assay sensitivities according to international and national guidelines for rapid Ag tests in general, requiring positive rate percentages ≥ 80, have frequently not been met [17,18].…”

“…between 91 and 100% [5][6][7][8][9][10][11][12][13][14][15][16]. While assay specificities were frequently found to be relatively high [5][6][7][8][9][10][11][12][13][14][15][16], assay sensitivities according to international and national guidelines for rapid Ag tests in general, requiring positive rate percentages ≥ 80, have frequently not been met [17,18]. Further, the studies published so far did not compare different automated SARS-CoV-2 Ag assays among each other, which will be critical for diagnostic laboratories seeking to implement such assays.…”

Diagnostic Performance of Automated SARS-CoV-2 Antigen Assay in Nasal Swab during COVID-19 Vaccination Campaign

“…The overall sensitivity of DiaSorin LIAISON SARS-CoV-2 Ag assay was evaluated to be 75.33% and the specificity reached 100%. Previous investigations of the LIAISON SARS-CoV-2 Ag test showed an overall sensitivity ranging from 31 to 84.8% and specificity of ≈100% at the 200 TCID 50 /mL manufacturer's cut-off [5,[24][25][26], whereas, when applying the cut-off at 82 TCID 50 /mL, a previous report showed that the sensitivity of the DiaSorin LIAISON SARS-CoV-2 Ag test yielded 73% sensitivity [26]. Moreover, similar automated antigenic assays have previously been evaluated and exhibited sensitivity ranging from 70% to 97% [21,22,[27][28][29][30][31][32][33].…”

“…Simpler and less expensive antigenbased tests have been developed to address these issues. However, antigen-detecting rapid diagnostic tests (Ag-RDT) require a visual readout and lack proper internal quality control, making them more prone to errors [5][6][7]. However, a number of automated antigendetecting diagnostic assays for SARS-CoV-2 detection are now commercially available and can result in rapid decisions on patient care, isolation and contact tracing at the point of care [8].…”