Validation testing to determine the effectiveness of lateral flow testing for asymptomatic SARS-CoV-2 detection in low prevalence settings

Abstract

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

Clarifying the evidence on SARS-CoV-2 antigen rapid tests in public health responses to COVID-19

“…Test underperformance was implied to explain finding only two positive results among 7189 individuals tested with Innova LFT. 25 In that study, 25 in a random sample of 710 (10%) LFT-negative individuals there were six PCR-positive results. That finding was extrapolated to 60 cases in the whole cohort, giving an extrapolated sensitivity of two of 62 (3•2%).…”

“…Early findings, widely reported, 3 from a study by Ferguson and colleagues, 25 suggested that LFT had only 3% sensitivity for detecting SARS-CoV-2 among PCR-positive students at Birmingham University. Test underperformance was implied to explain finding only two positive results among 7189 individuals tested with Innova LFT.…”

S-variant SARS-CoV-2 is associated with significantly higher viral loads in samples tested by ThermoFisher TaqPath RT-QPCR

“…A dataset of positive results from the first months of operation was released as a supplementary table in a recent publication comparing results of lateral flow device testing with RT-QPCR [3]. Raw Ct values from the supplementary table were analysed with respect to the presence of ORF-, N-, or S-gene target undetectable signals.…”

Multi-centre post-implementation evaluation of SARS-CoV-2 antigen-based point of care tests used for asymptomatic screening of continuing care healthcare workers

“…Many reports of asymptomatic SARS-CoV-2 testing campaigns using either APOCT or rRT-PCR tests have demonstrated low test positivity rates, suggesting high volume testing of asymptomatic individuals is of low yield [19][20][21][22]. Another Canadian study evaluating universal APOCT screening of HCWs in continuing care also found a similar APOCT positivity rate of 0.16% [23].…”