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Diagnostic performance of the Elecsys SARS‐CoV‐2 antigen assay in the clinical routine of a tertiary care hospital: Preliminary results from a single‐center evaluation
Author(s) -
Mueller Thomas,
Kompatscher Julia,
La Guardia Mario
Publication year - 2021
Publication title -
journal of clinical laboratory analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 50
eISSN - 1098-2825
pISSN - 0887-8013
DOI - 10.1002/jcla.23906
Subject(s) - medicine , antigen , immunoassay , covid-19 , virology , gastroenterology , immunology , antibody , disease , infectious disease (medical specialty)
Background This report describes a manufacturer‐independent evaluation of the diagnostic accuracy of the Elecsys SARS‐CoV‐2 antigen assay from Roche Diagnostics in a tertiary care setting. Methods In this single‐center study, we used nasopharyngeal swabs from 403 cases from the emergency department and intensive care unit of our hospital. The reference standard for detecting SARS‐CoV‐2 was the reverse‐transcription polymerase chain reaction (RT‐PCR) assay. Cycle threshold (Ct) values were recorded for positive RT‐PCR assays. The index test was the Elecsys SARS‐CoV‐2 antigen assay. This electrochemiluminescence immunoassay produces results as cutoff index (COI) values, with values ≥1.00 being reported as positive. Results Of the 403 cases, 47 showed positive results in RT‐PCR assays. Of the 47 RT‐PCR‐positive cases, 12 showed positive results in the antigen assay. Of the 356 RT‐PCR‐negative cases, all showed negative results in the antigen assay. Thus, the antigen assay showed a sensitivity of 26% (95% CI, 14%‐40%) and specificity of 100% (95% CI, 99%‐100%). Analysis of the relationship between Ct values and COI values in the 47 RT‐PCR‐positive cases showed a correlation coefficient of −0.704 (95% CI, −0.824 to −0.522). The true‐positive rate of the antigen assay for Ct values of 15–24.9, 25–29.9, 30–34.9, and 35–39.9 was 100%, 44%, 8%, and 6%, respectively. Conclusions The Elecsys SARS‐CoV‐2 antigen assay has a low sensitivity for detecting SARS‐CoV‐2 from nasopharyngeal swabs. Hence, we decided to not use this assay in the clinical routine of our hospital.

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