Comment fonctionne le nouveau test COVID-19 de 90 minutes ?

On 3^rd August, the UK government announced it would roll out two new rapid coronavirus tests ahead of winter. The tests - both able to detect the virus in less than 90 minutes - will be introduced to hospitals, care homes, labs, and a range of non-clinical settings.

As well as speeding up the process, the tests will be able to distinguish between COVID-19 and other winter viruses such as la grippe. Since these conditions have similar symptoms, but different implications (flu doesn't require self-isolation, for instance), it's important to get a diagnosis as soon as possible.

"We're using the most innovative technologies available to tackle coronavirus," said Health Secretary Matt Hancock. "Millions of new rapid coronavirus tests will provide on-the-spot results in under 90 minutes, helping us to break chains of transmission quickly. The fact these tests can detect flu as well as COVID-19 will be hugely beneficial as we head into winter, so patients can follow the right advice to protect themselves and others."

Why rapid testing is so important

The tests in question are a rapid swab test called LamPORE, and DNA testing machines called DnaNudge. According to the government, 450,000 of the LamPORE tests will be made available along with 5,000 DNA 'NudgeBox' machines. The latter will have the capacity to perform 5.8 million COVID-19 tests over the coming months.

Until recently, the UK has been relying on PCR swab tests, which need to be sent to a laboratory and take at least 24 hours to turn around. Dr William Haseltine, an infectious disease expert, has written two books about COVID-19: A Covid Back To School Guide et A Family Guide to Covid, which will be updated as our understanding of the virus evolves. As he explains, any test that simplifies diagnosis has advantages over current methods.

"The PCR tests and the new tests all detect viral infections using very different technologies," he says. "The PCR test is slower, most expensive and requires more highly trained personnel. The two new tests, which detect viral RNA, are simpler to use, use less expensive methods and produce answers more quickly."

He adds that convenience, price and speed will be essential going forward, as we move from testing those who think they've been exposed, to testing the general population. For instance, the LamPORE test may eventually be used to screen NHS staff, whether or not they have symptoms.

"Containment of the epidemic depends primarily on identifying those people who are contagious and isolating them from people who they might infect," says Dr Haseltine. "These tests are a first good step to identifying those who are contagious. I look forward to further improvements that make it even easier and less expensive than this current generation."

Dans his estimate, up to 90% of all people infected are asymptomatic. If true, this would further boost the case for widespread community testing - and quicker, cheaper tests.

How the tests work

The LamPORE test, developed by Oxford Nanopore, uses a technique called RT-LAMP, along with genetic sequencing, to identify the virus in a swab or saliva sample. Unlike the existing PCR tests, it can be processed on site through 'pop-up labs', further speeding up diagnosis.

The DnaNudge test, developed by the company of the same name, analyses DNA in nose swabs. It too can be used outside a lab, via the miniaturised NudgeBox analyser, and has an average sensitivity of 95% (similar to existing lab tests). At present, the machines are operating in eight London hospitals.

"We have been able to successfully adapt our in-store consumer DNA testing technology - which identifies genetic risks for chronic conditions related to l'obésité et diabète de type 2 - and validate it for detecting COVID-19 with gold-standard accuracy," said Regius Professor Chris Toumazou FRS, CEO and co-founder of DnaNudge.

Concerns about accuracy

Although both tests have been heralded as a breakthrough, some experts have raised concerns. When the rollout was first announced, there was no publicly available data on their accuracy, prompting fears that the government had rushed ahead without waiting for full evaluations.

"These tests should not be generally used without information available to the public regarding the sensitivity and specificity as well as the cost and speed of the test," says Dr Haseltine. "It is irresponsible to introduce these tests without release of underlying data that supports their use."

DnaNudge has since published a diagnostic accuracy study in The Lancet Microbe. Oxford Nanopore, meanwhile, says it has collaborated with multiple laboratories to evaluate LamPORE's performance. Approached for comment, a spokesperson said more information would become available in the coming weeks.

The future of COVID-19 testing

Both tests could make a real difference to the UK's testing capacity (as well as cutting down the nail-biting wait for results). However, there may be something even more ambitious in store. According to recent reports, the government is now working on a mass-testing regime nicknamed 'Operation Moon Shot', which would screen up to four million people every day. This would require cheap, rapid tests on an unprecedented scale.

This project is in the very early stages, and has been met with significant scepticism from some quarters. They point out that the government has repeatedly made promises about scaling up the Test and Trace programme, and has repeatedly failed to deliver. Assuming the new technology does turn out to be as fast, and as accurate, as its proponents hope, there is a huge logistical challenge involved in scaling up the tests.

Even if this could be achieved, the cost would be eye-watering. With vast amounts already spent on furlough and other measures, the Journal Médical Britannique has uncovered documents suggesting that the expansion of the programme would cost cost over £100bn to deliver - almost the same cost as the entire annual NHS budget.

However, if successful it would enable the country to control the virus without resorting to lockdowns. This would be crucial as we move into winter, both with regard to preventing and minimising a second wave and to preserving some normality.

In the meantime, it's important to abide by the existing advice - self-isolating and getting tested if you have symptoms.