Shortening turnaround time for high-priority patients during the COVID-19 epidemic: evaluation of the Xpert Xpress SARS-CoV-2 test

Abstract

Background: Although several molecular tests are now available for detecting SARS-CoV-2 RNA in nasopharyngeal swab samples, the number of requested tests exceeds the capacity of many diagnostic laboratories. Unfortunately, the available high-throughput platforms exhibit longer turnaround times than those required for management of high-priority patients.
 Methods: The aim of this study was to evaluate the performance and possible benefits of the Cepheid Xpert Xpress SARS-CoV-2 test, focusing mainly on turnaround time when applied to high-priority patients. We evaluated the Xpert Xpress SARS-CoV-2 test in comparison to the Roche’s cobas 6800 SARS-CoV-2 test by monitoring turnaround times and by retrospectively testing 20 nasopharyngeal swabs from COVID-19 patients with various viral loads. In addition, 50 patients were tested by both methods prospectively.
 Results: We observed a lower limit of detection of one SARS-CoV-2 genome equivalent/µL and 100% (95% CI, 92.6−100%) specificity and 95.5% (95% CI, 77.2−99.9%) sensitivity in comparison to the cobas SARS-CoV-2 test. When applying the Xpert Xpress SARS-CoV-2 test for high-priority patients the turnaround time could be greatly reduced, i.e. from 3 - 5 hours that take our routine diagnostics methods to about 1 hour.
 Conclusion: The novel Xpert Xpress SARS-CoV-2 test is a useful, easy to perform tool, valuable for rapid and reliable diagnosis of COVID-19, especially in high-priority patients when a short turnaround time is of key importance for further patient management.