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The lateral flow test bought by the British government for mass testing in Liverpool, and potentially across the country, could lose up to half of those who have Covid-19, according to experts.
The government has high expectations for the Innova test, having signed two contracts with the California-based company. Innova told the Guardian it now ships more than a million tests a day to the UK.
The Guardian understands that the government also hopes to use the test to shorten the duration of self-isolation among people identified as contacts of those with the coronavirus.
On Wednesday, the government released the results of an evaluation of lateral flow tests, which collect virus antigen from a nasal or throat swab or saliva within half an hour. He said they could be used to get the infection in people without symptoms.
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“An extensive clinical evaluation conducted by British Public Health and the University of Oxford shows that lateral flow tests are sufficiently accurate and sensitive to be used in the community, even for asymptomatic people,” the Department of Health said in a statement. health and social assistance.
He said the tests now deployed in Liverpool had 99.6% accuracy. “The results from PHE Porton Down and the University of Oxford show that the recently implemented lateral flow tests are highly reliable, sensitive and accurate in multiple settings,” he said. It had “an overall sensitivity of 76.8% for all PCR positive individuals, but detects over 95% of individuals with high viral loads.” PCR is the gold-standard swab assay that is widely used today but requires laboratory processing.
Professor Sir John Bell of the University of Oxford, a government advisor for life sciences, said the test could be used to detect infections in people who might not otherwise know they have one.
“The data in this validation report demonstrates that these cheap and easy-to-use tests can play an important role in our fight against Covid-19,” he said. “They identify those who can spread the disease and, if used systematically in mass testing, could reduce transmissions by 90%. They will detect the disease in a large number of people who have never even received a test before. “
But Professor Jon Deeks, an expert in evaluating Covid-19 tests, disagrees with their assessment of accuracy and said it would be dangerous to use the tests to rule out the disease.
A trial of the tests was carried out in a community testing center, where 58% of Covid-19 cases were detected. Another involved experienced nurses testing people in the hospital, which collected 73% of Covid-19 cases. Some were sent to Porton Down, where they raised 79%.
“For the first time, we are being allowed to see test performance data that the government has purchased for their Moonshot mass screening program. DHSC data shows that up to half of Covid cases can be ignored by the test, and can give more false positives than true positives when used in mass screening, “he said.
“I’m really worried that people aren’t being given information to understand what the results mean. A negative test indicates that your risk is reduced to between a quarter and half of the average, but does not rule out Covid. It would be tragic if people were misled into thinking they are safe to visit their elderly relatives or to take other risks.
“It is a basic epidemiology that tests that ignore cases such as Innova are not suitable for ruling out diseases, as is necessary for deciding whether students can return home safely at the end of the year. The government’s plan is wrong and dangerous at the same time.
“It appears that this data was not released before because it was not ready. The decisions to introduce mass testing do not appear to have been based on a serious examination of the evidence. “
Professor Sebastian Johnston of Imperial College London said the government’s announcement “gives the impression that all lateral flow antigen tests have high sensitivity after numerous clinical tests by PHE / Oxford. This is very far from the truth. “
Of the 40 tests evaluated, only one, Innova, was evaluated in detail. “Yes, it will be nice to have a single rapid test that can quickly detect people with high virus loads and quickly isolate them,” said Johnston. “This single test won’t be good enough to say you’re almost certainly negative, as its sensitivity isn’t good enough, especially in the hands of the general public.”
Peter Santeusanio, VP of Product Management at Innova Medical Group in California, told the Guardian that the ambition is for the tests to be used with saliva samples at home. People would use the smartphone camera to read the device and find out the results from an app.
“As far as I know today, we are the only antigen test that is used by the UK government as far as I know, fully validated for the saliva test,” he said.
“The saliva test is essential because the saliva test allows for testing at home. Finally. “
He believes lateral flow tests can be used to help people come out of isolation if they are negative. Two tests, two days apart, would be enough to tell if they are infected, he suggested. “Different people will have different protocols. But, in general, our position on this test is [if] take the first test and the first is negative, you would wait two days, take the second test. And if you’re still negative, you know, you’re probably fine, but if you want belt and braces, wait another two days. “
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