People in England without Covid-19 symptoms no longer need to take a polymerase chain reaction (PCR) test to confirm a positive lateral flow test (LFT).
The rule change came into effect on Tuesday morning to help with the UK’s widespread Covid-test shortages amid the Omicron variant outbreak.
With more reliance on LFTs, many are wondering just how accurate they are.
Here is all you need to know.
How accurate are lateral flow tests?
According to an October 2021 study from UCL, Liverpool University, Bath University, and Harvard, the accuracy of LFTs in detecting Covid-19 around 80%.
The study added that the figure rises to over 90% when those who have the virus are at their most infectious.
The likelihood of getting a false positive Covid-19 test result with a LFT is ‘extremely low’, according to a UK Health Security Agency spokesperson.
They previously told Metro.co.uk that, ‘The LFTs that we are using have a high specificity, that means the number of false positives are extremely low – less than 1 in 1,000 tests conducted from our studies.’
However, they added that false negatives, which is when you receive a negative result despite actually having Covid-19, are more common.
This is why PCR tests, which are more reliable, are still used in some instances – for example, when you test negative for Covid-19 despite having the symptoms.
How long do lateral flow tests last?
Any negative test results recorded in the NHS Covid pass app expire after 48 hours – while government guidance currently recommends taking a test ‘if you will be in a high-risk situation that day’.
However, experts are suggest that people should test immediately before going into any high-risk situation where they might infect others – as the Omicron variant is spreading so fast that a person can switch from being non-infectious to infectious ‘within hours’.
Irene Petersen, a professor of epidemiology at University College London, told The Telegraph: ‘We’re seeing so many examples now where people have taken a test a day before and then when they take one the day after they are positive.
‘Omicron is very, very fast, so the test result expires very quickly. It is hours that we are talking about now.’
Alan McNally, professor of Microbial Evolutionary Genomics at the University of Birmingham, also backed this up, explaining on Twitter: ‘If you have symptoms and are LFD (lateral flow) positive you have Covid. Don’t wait on PCR confirm to act. If you are LFD negative you still need to exercise caution. Protect yourself and others.
‘And use LFD just before you go out/visit. Not within 24 hours. Just before.’
How to order a lateral flow test
You can order free LFTs from the government website – the pack comes with seven tests.
However, there have been widespread shortages of the coveted tests in recent months.
If you are struggling to secure a test online, then you can try collecting some from the following:
- Pharmacies
- A community centre, such as a library
- Covid-19 test sites
A perk of collecting the tests in person is that you are allowed more to take two packs at a time, which is equal to 14 tests.
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