The evaluation of a multi-day testing approach with antigen lateral flow devices for people eligible for community-based COVID-19 treatments

Background COVID-19 therapeutics including antiviral and monoclonal antibody treatments (hereafter 'COVID-19 treatments') require rapid administration to be effective. As part of the community-based antiviral and therapeutic treatment pathway for COVID-19 there has been a move from PCR testing in those eligible to a rapid antigen lateral flow testing regime.Objectives To determine whether a multi-day lateral flow device (LFD) testing regime is a feasible alternative to PCR for diagnosing symptomatic patients eligible for COVID-19 treatments. An LFD regime might return a positive result more quickly than a PCR and hence expedite access to COVID-19 treatments.Methods A retrospective analysis was conducted of diagnostic testing for SARS-CoV-2 with a combination of PCR and LFDs of symptomatic patients eligible for COVID-19 treatments. LFD testing patterns were not assigned. Patients self-censored and the patterns were retro-fitted to the observed results.Results The LFD testing patterns offered high sensitivity, close to 92%; however, the false positive rate also increased, with most of the multi-day testing patterns having a false positive rate greater than 3%. The highest sensitivity was seen among patients who tested with LFD on the same day as PCR.Conclusions There were multiple observed testing behaviours. We conclude that multi-day LFD testing for COVID-19 provides a feasible alternative to PCR to in eligible patients, allowing swift prescription of COVID-19 treatments in most cases. This approach requires acceptance of a trade-off for a small increase in false-positive and -negative results.