Evaluation of ECLIA antigen detection tests as screening methods for COVID-19 in comparison with molecular analysis

• Published in: Irish journal of medical science Vol. 191; no. 5; pp. 2213 - 2217
• Main Authors: Kolesova, Olga, Tomassetti, Flaminia, Cerini, Paola, Finucci, Davide, Turchetti, Giordano, Capogreco, Francesca, Bernardini, Sergio, Calugi, Graziella, Pieri, Massimo
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.10.2022
• Subjects: Family Medicine; General Practice; Internal Medicine; Medicine; Medicine & Public Health; Original; Original Article; COVID-19; Antigen test; Molecular analysis; SARS-CoV-2; Diagnostic methodology
• ISSN: 0021-1265; 1863-4362
• DOI: 10.1007/s11845-021-02863-1

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.