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We don’t know how accurate the UK’s new rapid coronavirus tests are


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We don’t know how accurate the UK’s new rapid coronavirus tests are

By Jessica Hamzelou A billboard about covid-19 testing in Manchester, UKOLI SCARFF/AFP via Getty Images Two 90-minute tests for the coronavirus will be rolled out by the UK government in the coming weeks – and while both are promising, neither has publicly available data to support its use. Other independently verified rapid tests have been…

By Jessica Hamzelou

New Scientist Default Image

A billboard about covid-19 testing in Manchester, UK

OLI SCARFF/AFP via Getty Images

Two 90-minute tests for the coronavirus will be rolled out by the UK government in the coming weeks – and while both are promising, neither has publicly available data to support its use. Other independently verified rapid tests have been developed, say scientists who have been assessing the field.

Last week, the UK government announced that the two tests will, between them, provide more than 6 million coronavirus assessments to individuals at care homes and National Health Service hospitals across the UK.

But while the companies behind both tests say they have validated their accuracy, the details haven’t been published. “I’d never heard of these two tests,” says Jon Deeks at the University of Birmingham, UK, who has been comparing the evidence behind a range of rapid tests to diagnose covid-19.

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One of the tests was developed by DnaNudge, a company that already offers diet-based shopping advice for customers who share their DNA. The coronavirus test is based on a nasal swab, which is inserted into a disposable palm-sized cartridge. Up to 12 cartridges are then inserted into a machine the size of a shoebox, where a chemical reaction converts the virus’s RNA to DNA and makes multiple copies. Chemicals designed to seek out sequences from the coronavirus signal whether its is present.

“We developed the cartridge a few years ago… for the retail environment,” says Chris Toumazou, co-founder and CEO of DnaNudge. It was “very simple” to adapt the test for the coronavirus, he says.

The second test, developed by Oxford Nanopore Technologies, requires a lab or dedicated clean room for processing samples and feeding them into a machine the size of a desktop computer. A single machine can process 15,000 samples per day, says a spokesperson at the firm.

The spokesperson wouldn’t reveal the results of trials, or how accurate the test is when compared with standard tests. They told New Scientist that accuracy data is being prepared for publication.

Looking at data published before June, Deeks and his colleagues have identified only two rapid tests that have been assessed in independent studies: the Xpert Xpress test developed by Cepheid and Abbott’s ID NOW. The team is due to publish its findings soon, but more research is needed, says Deeks. Most of the tests seem to work well when samples contain a lot of virus, but perform poorly when faced with low viral loads, for example.

When asked why the UK government chose the DnaNudge and Oxford Nanopore tests, a spokesperson for Public Health England (PHE) stressed that it doesn’t validate or regulate tests. The spokesperson said PHE would have “been in the room” when the decision was made, but didn’t have the final say. They weren’t able to comment on the Cepheid or Abbott tests before publication.

Toumazou says that DnaNudge’s test has been validated. His team has been testing the diagnostic alongside standard NHS tests at English hospitals for the past two months, he says, and has shared the results with PHE and the UK’s Medicines and Healthcare products Regulatory Agency. MHRA told New Scientist that DnaNudge has an exceptional use authorisation, meaning the tests are allowed to be used clinically until October, but didn’t comment on the accuracy of the tests. PHE wasn’t able to respond to questions about accuracy before publication.

The DnaNudge test’s user guide states that it has 97 per cent sensitivity and 100 per cent specificity, meaning that 3 per cent of cases would be missed, and there were no false positive results. These figures are based on a study of 401 nasal swabs, 40 of which were excluded because they gave an invalid result, according to the user guide.

Both tests are promising, but without detailed published results, they cannot be properly scrutinised by the academic community, says Deeks.

Muhammad Munir at the University of Lancaster, UK, whose team has developed a separate, 30-minute diagnostic test for the coronavirus, agrees. New technologies need to be properly assessed before they can be employed, he says.

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