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Evaluation of ECLIA antigen detection tests as screening methods for COVID-19 in comparison with molecular analysis
Olga Kolesova1,2, Flaminia Tomassetti3,2, Paola Cerini2
1Department of Public Health and Infectious Diseases, University of Rome, La Sapienza, Rome, Italy.
Background:
Data from literature shows that antigen tests are rapid and helpful tools for diagnosis of COVID-19.
Aim:
This work aimed to evaluate the performances of the Elecsys SARS-CoV-2 Antigen test, in comparison to RT-qPCR, the gold standard.
Methods:
A total of 110 swabs were tested; according to rRT-PCR, 76 were positive, and 34 were negative. The swabs were processed by Elecsys SARS CoV 2 Antigen assay (Roche Diagnostics GmbH, Mannheim, Germany), an electrochemiluminescence immunoassay (ECLIA).
Results:
In a first evaluation, the overall sensitivity and specificity were 85% and 100%, respectively. It was noted that most of the discordant cases had cycle threshold (Ct) values > 28. Therefore, it was assumed a new measure to evaluate sensitivity and specificity, then samples with Ct values < 28 were selected. In this way, it was achieved a Ct < 28 sensitivity of 94%. The level of agreement between the two tests was 89. 1% with κ value of 0.77 for total data and 95.9% with κ value of 0.95 for samples with < 28 Ct. The antigen test performs well in the presence of high viral loads, whereas lower levels are missed.
Conclusions:
The comparison data obtained in this study support that this method seems a proper approach for rapid screening of patients with high SARS-CoV-2 viral load; however, the rate of sensitivity is highly Ct-dependent.
