Lateral Flow Tests Are 95% Effective at Detecting COVID-19 When Used Soon After Symptoms Start

A lateral flow Covid-19 test. Credit: Queen Mary University of London

A new study by researchers from Queen Mary University of London, University of Oxford, Institute for Advanced Studies, Vienna and the Medical University of Graz has shown that lateral flow tests detect COVID-19 with comparable accuracy to laboratory-based PCR tests, at provided they are used at the onset of an infection and shortly after symptoms begin.

Lateral flow tests are cheaper and provide a result in just 30 minutes – much faster than the time it takes to get a PCR test result, which can take 1-3 days. The finding could be crucial for national strategies to tackle the next phase of the pandemic, especially as timely and prompt testing will become even more important once current restrictions are lifted in England.

As part of the study, between October 22 and November 30, 2020, more than 2,500 people with mild to moderate flu-like symptoms were assessed by general practitioners in the district of Liezen (79,652), Austria, and tested for viral antigen using lateral flow. to test. Those suspected of having Covid-19 were also tested with a PCR test.

The lateral flow tests detected more than 95 percent of the cases found by PCR and correctly identified 89 percent of the cases as negative.

The study is the first to widely compare lateral flow and PCR testing on the same group of people. It also included the variables of a real-life situation: five different brands of test kit, three labs and professional swabs offered at 20 GP practices.

Research author Dr. Werner Leber of Queen Mary University of London said: “Previous studies have suggested that lateral flow tests may be less sensitive than PCR in detecting Covid-19, particularly in asymptomatic individuals and during the early or late stage of infection when the viral load is lowest. But we found that in patients who are newly symptomatic, the two testing methods have similar levels of accuracy.

“Countries are considering using lateral flow testing to manage future waves of the pandemic. Our findings support this step, but ensuring that tests are performed correctly should be an integral part of any strategy.

dr. Jasmina Panovska-Griffiths of the Big Data Institute and The Queen’s College at the University of Oxford added: “In our study, both shorter duration of symptoms and higher viral load were significantly associated with positive lateral flow tests. This highlights the need for testing in early infection with lateral flow tests, and shows that in patients who are newly symptomatic, the two test methods have comparable levels of accuracy.

“Our study is the first to demonstrate that point-of-care antigen testing using lateral flow testing combined with clinical assessment of symptomatic patients can quickly and accurately detect SARS-CoV-2 infection in primary care. “

dr. Thomas Czypionka of the Institute for Advanced Studies, Vienna, said: “The research results form the basis for future containment strategies in primary care, which can make an important contribution to the management and prevention of a pandemic. In the context of future easing of lockdown rules, in addition to vaccinations, early detection of people with infection through reliable testing will be necessary to control COVID-19.”

Prof. dr. dr. Andrea Siebenhofer, from the Institute of General Practice and Evidence-based Health Services Research, Medical University Graz, said: “This study was the first in Styria where GPs were actively involved in the research process. Research from practice for practice and with a result that can directly contribute to optimizing care during the COVID-19 pandemic.”

In summary, this study provides evidence that lateral flow testing can accurately detect SARS-CoV-2 infection as an alternative to PCR testing in symptomatic patients in a true primary care setting over a wide geographic area.

Reference: “Comparing the diagnostic accuracy of point-of-care lateral flow antigen testing for SARS-CoV-2 with RT-PCR in primary care (REAP-2)” by Werner Leber, Oliver Lammel, Andrea Siebenhofer, Monika Redlberger-Fritz and Jasmina Panovska-Griffiths, July 13, 2021, EClinicalMedicine.
DOI: 10.1016/j.eclinm.2021.101011

The study was funded by the European Union’s Horizon 2020 Research and Innovation Program (Grant Agreement No. 101016233 (PERISCOPE).