COVID-19: Lateral Flow Tests 'Rival Lab-based Testing' 

Peter Russell

July 14, 2021

Lateral flow tests (LFTs) were found to be an accurate alternative to laboratory-based PCR tests for detecting COVID-19, providing they were used at the onset of infection with SARS-CoV-2 and soon after the onset of symptoms, researchers said.

The observational study, in EClinicalMedicine , published by The Lancet, suggested that concerns over the accuracy of LFTs might be misplaced.

'Real World' Setting

The research was based on 2562 symptomatic patients assessed by GPs in the district of Liezen, Austria, between October 22 and November 30, 2020.

Those who exhibited mild to moderate flu-like symptoms, including fever, cough, runny nose, sore throat, earache, diarrhoea, or a general feeling of illness, were tested using one of five viral antigen LFTs, all of which met World Health Organisation minimum performance standards.

Those whose symptoms suggested an alternative diagnosis, including glandular fever illness, bacterial tonsillitis, and otitis media were excluded from the study. The remaining participants were tested using a PCR test.

Overall sensitivity for the LFT tests was 95.4% of the cases found by PCR, with a specificity of 89.1%.

The researchers, from Queen Mary University of London (QMUL), the University of Oxford, Institute for Advanced Studies, Vienna, and the Medical University of Graz, said the study was the first to compare LFTs and PCRs on the same group of people and at a large scale.

In addition to using different LFT kits, their research also involved professional swabbing at 20 different GP practices, and the assistance of three laboratories.

'Important Contribution' to Pandemic Control

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

The researchers pointed out that LFTs are cheaper to administer and produce a result within 30 minutes compared to PCR tests that require laboratory assessment, with results delayed by 1 to 3 days.

Dr Jasmina Panovska-Griffiths from the Big Data Institute and 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 necessity of testing at early infection with lateral flow tests, and shows that in patients who are newly symptomatic, the two testing methods have similar levels of accuracy."

Dr Thomas Czypionka from the Institute for Advanced Studies, Vienna, commented: "The study results provide the basis for future containment strategies in primary care, which can make an important contribution in control and prevention of a pandemic.

"In the context of future relaxations of lockdown rule – in addition to vaccinations – the early detection of people with infection through reliable tests will be necessary in order to control COVID-19."

The study was funded by the European Union's Horizon 2020 Research and Innovation Programme

Comparing the diagnostic accuracy of point-of-care lateral flow antigen testing for SARS-CoV-2 with RT-PCR in primary care (REAP-2)’. Werner Leber, Oliver Lammel, Andrea Siebenhofer, Monika Redlberger-Fritz, Jasmina Panovska-Griffiths, Thomas Czypionka. EClinicalMedicine. DOI 10.1016/j.eclinm.2021.101011

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