Extrapolation of United Kingdom Pillar 2 Care home Covid-19 test data to ascertain effectiveness of lateral flow testing in low prevalence settings

Ferguson, Jack; Dunn, Steven; Best, Angus; Mirza, Jeremy; Percival, Benita; Mayhew, Megan; Megram, Oliver; Ashford, Fiona; White, Thomas; Moles-Garcia, Emma; Plant, Tim; Bosworth, Andrew; Kidd, Mike; Richter, Alex; Deeks, Jonathan J; McNally, Alan

Lateral flow devices are quickly being implemented for use in large scale population surveillance programs for SARS-CoV-2 infection in the United Kingdom. These programs have been piloted in city wide screening in the city of Liverpool, and are now being rolled out to support care home visits and the return home of University students for the Christmas break. Here we present data on the performance of Lateral Flow devices to test almost 8,000 students at the University of Birmingham between December 2nd and December 9th 2020. The performance is validated against almost 800 samples using PCR performed in the University Pillar 2 testing lab, and theoretically validated on thousands of Pillar 2 PCR testing results performed on low-prevalence care home testing samples. Our data shows that Lateral Flow Devices do not detect infections presenting with PCR Ct values over 29-30, meaning that only 3.2% (95% CI 0.6% to 15.6%) of total cases in the student population were detected, but that as many of 85% of cases tested in the Pillar 2 PCR lab would have been detected theoretically