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Evaluation confirms accuracy of rapid Covid-19 tests

Image: Governor Tom Wolf [CC BY 2.0], via Flickr

Innova test deployed in Liverpool is ‘sensitive enough’ for broader use and asymptomatic testing

Rapid Covid-19 tests deployed as part of a two-week whole-city pilot in Liverpool have been found to be highly effective and could help the UK return to normality, the government has said.

Lateral flow tests are rapid turnaround tests that can process Covid-19 samples on site without the need for laboratory equipment, with most generating results in under half an hour.

According to a clinical evaluation published on 11 November, the Innova lateral flow tests used in Liverpool are accurate and sensitive enough to be used in the community, including for asymptomatic people, with over 99.6 per cent specificity.

Public Health England’s Porton Down lab and the University of Oxford evaluated 40 different lateral flow devices. The evaluation showed that four of those had a sensitivity of more than 70 per cent of all PCR-positive cases and caught all cases with high viral loads, meaning they were effective in identifying those who were infectious and most likely to transmit the disease.

The evaluation concluded that the tests should be used in asymptomatic testing, as they offered the advantage of reducing risk and increasing capacity.

Health innovation minister James Bethell said the government was “absolutely committed” to using the latest testing technology to make asymptomatic testing available in more areas. “It is right we’ve taken a dual-track approach to evaluating this technology—by piloting them in the field so we can understand how best to make these tests available, and by getting our world-leading academics and clinicians to undertake rigorous evaluation of their ability to detect the virus,” he said.

“I’m delighted that both are already demonstrating that lateral flow tests can be the reliable, highly sensitive technology we need to help get this virus under control and return to as close to normality as possible.”

John Bell, professor of medicine at the University of Oxford, said: “The data in this validation report demonstrates that these inexpensive, easy-to-use tests can play a major role in our fight against Covid-19.”

Other academics have generally welcomed the findings. Jonathan Ball, a professor of molecular virology at the University of Nottingham, said: “Whilst the lateral flow assay lacks the sensitivity of the PCR test, its rapidity and ease of use makes it a pragmatic test for community surveillance, where you want to quickly identify then isolate infected people.

“Even though it won’t detect as many infected individuals as the PCR test, it will identify those with the highest viral loads, and it’s those people who are most likely to go on to infect others. It won’t replace other tests like PCR, but it is a useful additional tool for coronavirus control.”

Sebastian Johnston, a professor of respiratory medicine and allergy at Imperial College London, described “the high specificity” of the Innova test as “relatively good news as it means relatively few people who do not have Sars-Cov-2 infection will have to isolate unnecessarily”.

However, “that is still 32 people for every 10,000 people tested having to isolate unnecessarily. I would not wish to be one of those 32.”