Validation testing to determine the sensitivity of lateral flow testing for asymptomatic SARS-CoV-2 detection in low prevalence settings: Testing frequency and public health messaging is key

Abstract

Lateral flow devices (LFDs) 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 LFDs to test almost 8,000 students at the University of Birmingham between December 2 and December 9, 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 show that LFDs do not detect infections presenting with PCR Ct values over 29 to 30 as determined using the Thermo Fisher TaqPath asssay. This may be of particular importance in detecting individuals that are either at the early, or late stages of infection, and reinforces the need for frequent, recurrent testing.

Performance of the Innova SARS-CoV-2 antigen rapid lateral flow test in the Liverpool asymptomatic testing pilot: population based cohort study

“…Some concerns remain about the use of LFT, however, most noticeably about the accuracy reported by selftrained or non-expert readers in the asymptomatic population. 9 On 6 November 2020 a community testing programme, piloted in Liverpool and sponsored by the Department of Health and Social Care, started with the aim of identifying more infected people earlier in their infection cycle so they could self-isolate and break transmission chains. To assess the performance and appropriate implementation of the Innova LFT in Liverpool, we performed a quality assurance exercise.…”

“…The PHE evaluation2 indicated that LFT was able to identify more than 90% of people with a Ct <25, corresponding approximately to a viral load of >10 5 RNA copies/mL, indicating that the LFT has the potential to identify most of those who are infectious. Some concerns remain about the use of LFT, however, most noticeably about the accuracy reported by self-trained or non-expert readers in the asymptomatic population 9…”

Cost-effectiveness of a whole-area testing pilot of asymptomatic SARS-CoV-2 infections with lateral flow devices: A modelling and economic analysis study

“…Initial reports from the Liverpool pilot reported the true positive rate of LFD tests was 99.9%, but a false negative rate of 48.9% [ 6 ]. A recent study of LFD tests in UK university students found sensitivity was estimate the sensitivity can be as low as 3% [ 7 ]. The sensitivity of the test is highly dependent on the expertise of who the test is administered by [ 8 ].…”

“…The sensitivity of the test is highly dependent on the expertise of who the test is administered by [ 8 ]. LFD tests sensitivity is significantly influenced by viral load [ 7 ]. Viral load peaks in asymptomatic cases are lower than for symptomatic cases, affecting the usefulness of LFDs as a screening tool.…”

Evaluation of the clinical performance of a magnetic force-assisted electrochemical immunoassay for the detection of SARS-CoV-2 antigens

“…Nevertheless, if sufficient accuracy is obtained, then rapid antigen tests may replace RT-PCR based tests as a means for triaging or may play a role in rapid determination. Furthermore, rapid Ag tests can be easily delivered to the site, and they can be used for the mass screening of COVID-19 patients and in a more targeted manner at airports, schools, and international/regional borders [ 18 , 19 ].…”