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5 Nov 2020

The problem with rapid COVID-19 tests

COVID-19 swab tests with near-instant results - such as those launched by Boots - hold promise, but important questions remain

COVID-19 swab tests that give you results in less than 15 minutes have been making the news again recently - but the same drawbacks that have accompanied previous attempts at rapid testing remain, and caution is required.

Last week, Boots announced its £120 12-minute rapid swab test, set to launch this month. And on Saturday, the government made its latest promise to do a 'mass testing rollout' - this time with home self tests that give you results in 10-15 minutes, but the launch date is still to be confirmed.

The desire for widely available testing and quick results is understandable, but there are important issues with these tests that need to be ironed out and serious public health considerations that get skipped over in the race for rapid testing.

The growing number of pricey private coronavirus tests on sale also threatens to deepen inequalities in access to healthcare and create confusion for consumers - including the possibility of false reassurance about their health.

COVID-19 testing: what your options are and what to be wary of

What is the Boots 12-minute coronavirus test?

This test, which is not yet available but coming soon, is billed by Boots as a convenient way for people to check for a current infection before 'attending an event or seeing family' (subject to lockdown rules) and reducing 'inappropriate' use of the NHS testing system.

It's done by taking a nasal swab sample, which is then analysed by a healthcare professional on the spot using a point-of-care testing device and results are available within 12 minutes.

Boots says the test is not suitable for people with symptoms or who think they might have COVID-19. These people should seek a free test through the NHS.

However, the test manufacturer (LumiraDx) says on its website that the intended use for the test is 'individuals suspected of COVID-19 by their healthcare provider within the first twelve days of symptom onset'.

According to the website, the test has only been tested in one company study and only on symptomatic cases.

When we asked Boots, it told us that 'LumiraDx conducted a study on 500 patients, including a population of symptomatic positive and negative patients, and asymptomatic 'at risk' patients. Specificity on a group of 100 'at risk' asymptomatic patients came out at 99% accurate'.

That 99% 'specificity' figure gives us an idea of the rate of false positive results, but we also need to know about sensitivity - the rate of false negatives - to get an understanding of the accuracy of these tests. These details aren't publicly available.

Boots told us it's seeking further information and that the rapid test is going through additional internal due diligence processes prior to being offered in store.

What can a rapid COVID-19 test tell you?

woman taking covid swab test

The broader problem with this kind of rapid test is that they may struggle to detect asymptomatic infections, so a negative result isn't robust enough to let you change your behaviour.

While a swab test can indicate whether you were infected at the time of the test and provide some peace of mind, it's still possible you could develop COVID-19 soon after.

So it's not as if you can take one of these and then visit elderly or vulnerable relatives with impunity, as some have suggested.

The LumiraDx leaflet states that 'a false negative result may occur if the level of viral antigen in a sample is below the detection limit of the test or if the sample was collected inappropriately, therefore a negative test result doesn't rule out the possibility of infection'.

Jon Deeks, Professor of biostatistics at Birmingham University, told us that at the moment all these rapid results tests have only been approved for sale to people who have symptoms and haven't been approved for sale to people who don't have symptoms.

He said: 'This type of test is known to miss lower levels of virus. We don't know whether they can pick up early infection and asymptomatic infection, both of which can still be infectious. If you have symptoms you are, of course, eligible (and should) get a free PCR test through the government testing service.'

Government announces rapid coronavirus test plans

Boris Johnson has promised a mass rollout of rapid tests would tell you whether you're currently infected within 10 to 15 minutes that you can perform yourself at home.

He said that these tests could be applied in'an ever-growing number of situations, from helping women to have their partners with them in labour wards when they're giving birth to testing whole towns and even whole cities'.

The first city-wide rapid testing trial is underway in Liverpool - intended to identify as many infected people as possible, including those without symptoms. This will be done with a combination of the existing NHS swab tests and these new rapid turnaround tests.

Secondary school students in England are also set to receive these tests in January.

This test is also done with a nasal swab, or a throat swab, which is analysed on the spot with a test cartridge similar to a pregnancy test.

But these rapid turnaround tests are beset with similar usability issues to the Boots test.

Innova, the manufacturer of the test, says on its website that the intended use for these tests is for patients within five days of symptom onset and should be performed by trained healthcare professionals.

Indeed, initial results from the Liverpool pilot are not exactly promising. A report published in the BMJ revealed that the tests had picked up just 49% of asymptomatic Covid cases as compared to a PCR swab test (which is the main one you can currently get on the NHS and takes a few days to return results).

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Unclear testing landscape confusing for consumers and unhelpful for public health efforts

The launch of private COVID-19 testing services at both Boots and Superdrug in recent weeks only adds to the confusing raft of private tests being increasingly marketed to the public.

This is concerning as the different types of tests being touted can be difficult for consumers to navigate. Understanding the nuances of specificity and sensitivity figures between different tests - and what they are actually able to tell you - is no simple task.

COVID-19 testing kits are classed as medical devices, which come under the regulation of the Medicines and Healthcare products Regulatory Agency (MHRA). For a medical device to be safe to use, it must have a valid CE mark (the manufacturer's claim that a product meets appropriate regulatory requirements), but even coronavirus tests with CE marks can have limitations.

The MHRA has investigation and enforcement powers in relation to safety and quality of medical devices in the UK, but it's unclear exactly what is being done in terms of assessment and regulation of these rapid tests.

When we raised the issue of this new Boots swab test with them, it didn't comment and referred us to the Department of Health and Social Care, which has also yet to respond.

Public Health England (PHE) advice, published in May 2020, advises community pharmacies against offering rapid covid tests, stating that: 'it is not yet known if a positive or negative result is reliable'.

Health test kits: what you need to know- we assessed a range of self-testing kits earlier in 2020 and found some worrying issues