Evaluation of a multi-day testing approach with lateral flow devices for SARS-CoV-2

Background Due to the increase in COVID-19 cases with the emergence of new variants of concern in late 2021, a key area of interest was whether alternative forms of testing could be used as a contingency should polymerase chain reaction (PCR) testing capacity be breached. This evaluation sought to determine if repeat antigen testing was sufficiently sensitive enough to be used as an alternative to PCR. Methods People attending NHS Test and Trace sites for PCR testing were invited to participate and supplied with lateral flow device (LFD) test kits. They were asked to take a test the same day (day 0), and one test per day for the subsequent two days and upload their results using the national COVID-19 reporting system. Participants were assigned a posteriori to five different hypothetical testing patterns and results were used to infer the accuracy of potential multi-day LFD testing patterns in comparison to a single PCR test. Findings Of 2792 recruited participants, 1773 had evaluable PCR and LFD results and were included in the analyses. Multi-day LFD testing patterns that involved testing on days 0 and 2 (relative to PCR testing), or day 0, 1 and 2 offered high sensitivity with the 95% lower confidence limit (LCL) exceeding the 92% non-inferiority threshold. There was not enough evidence to conclude that same day testing (day 0 only) or testing on day 0 and 1 was non-inferior to the single PCR test. Conclusion Multi-day LFD testing for COVID-19 provides a feasible alternative to PCR testing in community-based settings, with earlier detection in most cases.