ABSTRACT
Background: The Innova SARS-CoV-2 antigen rapid lateral flow test (LFT) offers fast detection of COVID-19 cases. This study assesses the performance of LFT in the general population attending asymptomatic testing centres.Methods: Observational cohort study to compare LFT with reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) results based on two self-administrated swab samples per participant taken within minutes among individuals declaring no classic symptoms, attending asymptomatic testing sites in Liverpool, UK, between 6th and 29th of November 2020.Findings: 5869 individuals attended 48 testing sites in Liverpool. The relative sensitivity of LFT versus RT-qPCR, excluding void tests, was 40∙0% (95% CI: 28∙5 to 52∙4; 28/70). The specificity was 99∙9% (99∙8 to 99∙99; 5431/5434), positive predictive value was 90∙3% (74∙2 to 98∙0; 28/31) and negative predictive value was 99∙2% (99∙0 to 99∙4; 5431/5473). For cases with RT-qPCR cycle threshold CT <18∙3 (approximate viral loads > 10 6 RNA copies/ml), sensitivity was 90∙9% (58∙7 to 99∙8; 10/11), for CT <24∙4 (viral load > 10 4 RNA copies/ml), sensitivity was 69∙4% (51∙9 to 83∙7; 25/36), and for CT >24∙4 (viral load <10 4 RNA copies/ml), sensitivity was 9∙7% (1∙9 to 23∙7; 3/34).Interpretation: Innova LFT is a helpful tool for identifying infections among people who declare no symptoms of COVID-19, particularly those with high viral load and so more likely to infect others. The number of cases with lower CT (indicating higher viral load) missed by LFT, although small, should be considered, with due caution over using single LFT in high-consequence settings. Clear and accurate communication with the public about how to interpret test results is important. Further research is needed to understand how infectiousness is reflected in the viral antigen shedding detected by LFT versus the viral loads approximated by RT-qPCR.Funding: This evaluation was commissioned by the UK Department of Health and Social Care.Declaration of Interests: This evaluation was commissioned by the UK Department of Health and Social Care. IEB, MGF, MGS, DMH, GB and CPC received grant funding from the UK Department of Health and Social Care to evaluate LFT in the Liverpool pilot discussed in this article. IEB reports fees from AstraZeneca as chief data scientist adviser via Liverpool University and a senior investigator grant from the National Institute for Health Research (NIHR) outside the submitted work. MGS is Chair of the Infectious Disease Scientific Advisory Board and a minority shareholder in Integrum Scientific LLC, Greensboro, NC, USA, a company that has interests in COVID-19 testing but not with lateral flow technology, and reports grants from the NIHR, the Medical Research Council, and the Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool.Ethics Approval Statement: The University of Liverpool provided secondary data analysis as part of a UK national service evaluation with data collection by the UK Department of Health and Social Care (DHSC; Sponsor) As per the National Health Service (NHS) Research Authority guidelines, this work did not require ethical approval.