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

Abstract

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.

Severe acute respiratory syndrome coronavirus 2 antibody prevalence in adult patients with short bowel syndrome—A German multicenter cross‐sectional study

“…Patient blood was then tested for antibodies against the N antigen for SARS‐CoV‐2 by the respective clinic laboratory (Elecsys Anti‐SARS‐CoV‐2; F. Hoffmann‐La Roche Ltd). Published false‐positive rates were between 0% and 0.2% 12,13 . Patients filled out a questionnaire with information regarding their digestive anatomy, parenteral support, frequency of medical personnel visits, current respiratory symptoms, course of potential or proven COVID‐19 disease, occupation, household situation, the willingness to take risks (on a scale of 0–10, where high scores indicate riskier behavior) and level of worry due to COVID‐19 concerning the economy, personal finances, transmission of SARS‐CoV‐2, insufficient treatment, and lack of medical or general supplies.…”

“…Published false‐positive rates were between 0% and 0.2%. 12 , 13 Patients filled out a questionnaire with information regarding their digestive anatomy, parenteral support, frequency of medical personnel visits, current respiratory symptoms, course of potential or proven COVID‐19 disease, occupation, household situation, the willingness to take risks (on a scale of 0–10, where high scores indicate riskier behavior) and level of worry due to COVID‐19 concerning the economy, personal finances, transmission of SARS‐CoV‐2, insufficient treatment, and lack of medical or general supplies. The status of vaccination was documented at the time of presentation and patients were defined as fully vaccinated 2 weeks after the second dose.…”