What is a lateral flow test and where to get lateral flow test kits?

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  • All adults in England can now get a free lateral flow test twice weekly as part of the government’s roadmap out of lockdown

    Lateral flow tests have been used since schools reopened in early March to test for whether someone might have Covid-19, but be asymptomatic. From April 9 2021, everyone in the UK is being offered two tests per week. This is in the hope of preventing another spike in coronavirus cases as lockdown restrictions ease.

    But what is a lateral flow test? How do they differ from other Covid tests and where can you get them from?

    What is a lateral flow test?

    Lateral flow tests are hand-held devices with an absorbent pad at one end and a small window for the reading on the other side. Inside the test is a strip of test paper that changes colour when Covid-19 proteins (antigens) are detected. 

    You take a sample from the back of your throat with the swab, near the tonsils and from the nose. This swab is then dipped into a solution to extract the proteins. The solution is dripped onto the device’s testing pad and the reaction on the paper gives the result.

    Picture of a negative lateral flow test

    A lateral test device. (Credit: Getty)

    If the result is negative, one line next to the ‘C’ on the external casing of the test will appear. But if the result is positive, two lines will appear. One is next to the ‘C’ and the other is next to the ‘T’. 

    Results on lateral testing devices are quick – often available precisely 30 minutes after the solution is applied. 

    Anyone who tests positive for coronavirus with the lateral flow test must follow self-isolation rules immediately and inform the NHS of the test result. They should then confirm the result with a PCR test as soon as possible. 

    A negative result means that an active coronavirus infection was not found at the time of the test. But, it doesn’t guarantee that you don’t have the virus. It’s still important to follow social distancing guidelines, wash your hands frequently and wear a face covering.

    Where to get lateral flow tests

    There are five options for where you can pick up a free lateral flow test:

    • From the home ordering service, which allows people to order lateral flow tests online to be delivered to them.
    • Workplace testing schemes, either on-site or at home.
    • Community testing sites, now being offered by all local authorities.
    • A local PCR test site during specific test collection time windows, for collection only.
    • On-site testing facilities at schools and colleges.

    While these are now available to the general population now, anyone attending or working at an educational establishment, or living with someone who does, has been able to get a home test via the government’s website.

    The change to allow everyone to access a lateral flow test from home comes “as we continue to make good progress on our vaccine programme and with our roadmap to cautiously easing restrictions underway,” Boris Johnson said.

    “Regular rapid testing is even more important to make sure those efforts are not wasted.

    “That’s why we’re now rolling out free rapid tests to everyone across England – helping us to stop outbreaks in their tracks, so we can get back to seeing the people we love and doing the things we enjoy.”

    The tests are free to pick up for everyone, no matter where or how you pick them up.

    How accurate are lateral flow tests

    The Innova test – which is the lateral flow test being used in the UK – was found to be more than 95% effective at detecting Covid-19 in people with “high viral loads”.

    Woman taking lateral flow test at test site

    Credit: Getty

    This result comes from a mass-testing pilot scheme conducted in Liverpool last year by PHE England Oxford University. It has not yet been peer-reviewed yet, but the research did suggest that the test accurately identified more than 95% of these highly infectious individuals.

    When it comes to identifying Covid-19 in those who don’t have high viral loads, though, the result is very different. Health Secretary Matt Hancock originally said that lateral flow tests are 70% effective at detecting Covid-19 proteins in people who are not showing symptoms of coronavirus. This number came from research by the Porton Down lab and the University of Oxford, carried out in November last year.

    They found that the “overall sensitivity” of the test was 76.8%. Over 95% of people with high “viral loads” were detected by the test.  

    However, this is disputed by a SAGE report which reveals that lateral flow tests were only 48% accurate at picking up the Covid-19 proteins. The report compared the performance of the lateral flow tests used in the mass-testing pilot scheme in Liverpool last year, with the PCR tests that the UK uses as standard for people with symptoms. 

    With such disparity, it’s fair to ask where this huge difference comes from. And importantly, which number is correct? 

    The Porton Down and University of Oxford teams, who conducted the research cited by Matt Hancock, found that the lateral flow tests were most accurate (79%) when they were carried out by the lab’s scientists, followed by trained healthcare workers (73%). They were the least accurate when conducted by “self-trained members of the public” (58%). 

    Lateral flow test being developed

    Credit: Getty

    The lower percentage is a lot closer to the 48% given by the SAGE report. This suggests that lateral flow tests tend to be less accurate when they are conducted by members of the public. 

    This means that when the home self-tests are being conducted, they are likely to be less than 70% effective. The chances of finding a positive case will increase, however, when the second lateral flow test is conducted three days afterwards.

    Who can have a lateral flow test?

    From April 9, anyone over 18 years old can have a lateral flow test. They must not have symptoms of Covid-19 and to use the new scheme, should not be in full time education.

    Those who do have symptoms should self-isolate immediately and order a PCR test instead.

    Boris Johnson urged, “Please use the free NHS tests – even if you don’t feel ill. Because remember, 1 in 3 people with this virus doesn’t have any symptoms.”