Comparative evaluation of four SARS-CoV-2 antigen tests in hospitalized patients

Objectives: Rapid identification of infected subjects is a cornerstone for controlling a pandemic like the current one with the SARS-CoV-2. Easy to handle antigen tests can provide timely results, which is of particular importance in a primary care setting. However, concerns exist regarding their sensitivity, which led us to evaluate four commercially available tests in patients hospitalized for COVID-19. Methods: We analyzed in parallel nasopharyngeal/oropharyngeal swabs from 154 consecutive patients admitted to our department with moderate to severe COVID-19, using quantitative RT-PCR (Cobas, Roche) and up to four antigen tests from different distributors. Antigen test results were linked to Ct (cycle threshold) values as markers for patients' infectivity. Results: We found that two out of four antigen tests correctly identified subjects with high viral loads (Ct 25), and three out of four tests detected more than 80% of subjects with a Ct 30, which is considered the threshold for infectivity. However, one test investigated had a poor clinical performance. When investigating subjects with Ct values >30, we found that the antigen test was still positive in up to 45% of those cases. Conclusion: Most antigen tests had a sufficient sensitivity to identify symptomatic subjects infected with SARS-CoV-2 and with transmissible infection. On the other hand, antigen testing may not be suitable to identify loss of infectivity in COVID-19 subjects during follow-up. Newly introduced antigen tests need to be validated in a clinical or primary care setting to define their clinical usefulness. (C) 2021 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.

Automated summary

The study evaluated the clinical performance of four commercially available antigen tests in hospitalized COVID-19 patients. Most antigen tests had sufficient sensitivity to identify subjects infected with SARS-CoV-2 and with transmissible infection, but may not accurately identify patients who have lost infectivity.