Real-world evaluation of COVID-19 lateral flow device (LFD) mass-testing in healthcare workers at a London hospital; a prospective cohort analysis

Objectives: Real-world evaluation of the performance of the Innova lateral flow immunoassay antigen device (LFD) for regular COVID-19 testing of hospital workers. Methods: This prospective cohort analysis took place at a London NHS Trust. 5076 secondary care health-care staffparticipated in LFD testing from 18 November 2020 to21 January 2021. Staffmembers submitted results and symptoms via an online portal twice weekly. Individuals with positive LFD results were invited for confirmatory SARS CoV-2 PCR testing. The positive predictive value (PPV) of the LFD was measured. Secondary outcome measures included time from LFD result to PCR test and staffsymptom profiles. Results: 284/5076 individuals reported a valid positive LFD result, and a paired PCR result was obtained in 259/284 (91.2%). 244 were PCR positive yielding a PPV of 94.21% (244/259, 95% CI 90.73% to 96.43%). 204/259 (78.8%) staffmembers had the PCR within 36 hours of the LFD test. Symptom profiles were confirmed for 132/244 staffmembers (54.1%) with positive PCR results (true positives) and 13/15 (86.6%) with negative PCR results (false positives). 91/132 true positives (68.9%) were symptomatic at the time of LFD testing: 65/91 (71.4%) had symptoms meeting the PHE case definition of COVID-19, whilst 26/91 (28.6%) had atypical symptoms. 18/41 (43.9%) staffmembers who were asymptomatic at the time of positive LFD developed symptoms in the subsequent four days. 9/13 (76.9%) false positives were asymptomatic, 1/13 (7.7%) had atypical symptoms and 3/13 (23.1%) had symptoms matching the PHE case definition. Conclusions: The PPV of the Innova LFD is high when used amongst hospital staff during periods of high prevalence of COVID-19, yet we find frequent use by symptomatic staff rather than as a purely asymptomatic screening tool. LFD testing does allow earlier isolation of infected workers and facilitates detection of individuals whose symptoms do not qualify for PCR testing. (C) 2021 The British Infection Association. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study evaluated the performance of the Innova lateral flow immunoassay antigen device in real-world settings among hospital workers, showing a high positive predictive value during periods of high COVID-19 prevalence. LFD testing allows for earlier isolation of infected individuals and detection of symptomatic cases that may not qualify for PCR testing.