Covid lateral flow tests are reliable for detecting infections in asymptomatic people and should not need to be confirmed by a PCR test, an expert in microbiology has told ITV News.
Speaking to Deputy Political Editor Anushka Asthana, Professor Alan McNally, Director of the Institute of Microbiology and Infection at Birmingham University, said it has been the right time “for a long time” to shift away from the frequent use of "expensive" and time-consuming PCR tests towards easier and faster lateral flow tests.
Covid testing rules are changing across the UK so symptomless people who get an initial positive result on their lateral flow test won't need a PCR test to begin their period of self-isolation.
“We've been doing hundreds of thousands of really expensive PCR tests everyday, and they haven’t really had an impact on the pandemic since last summer,” Prof McNally said.
“We've had lateral flows now for the best part of six or seven months, everyone’s comfortable with using them, they’re easy to do, it’s an instant result and almost no false positives known of, so this is the right move,” he added.
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The changes, which have come into force across all of the UK, will in theory allow people to get back to work earlier, having begun their period of quarantine as soon as they received one positive result.
Capacity in laboratories processing PCR results should also increase, as they'll only be fielding tests from those people with symptoms.
The rule changes also follow weeks of disruption to the supply of Covid tests across England.
ITV News Health Editor Emily Morgan explains the key reasons behind the new changes
Health experts and scientists have welcomed the move saying it is the right way to proceed, with some saying it should have been brought in earlier given the accuracy of lateral flow tests.
“If you have symptoms and your lateral flow is positive you have Covid and you’re just flooding an already flooded system with more requests for tests, it makes no sense,” Prof McNally said.
But he added that this doesn’t mean PCR tests should be completely got rid of, but that they should be used in a more focused way “to support healthcare workers, care home staff, the most clinically vulnerable people”.
While there have been some questions about the safety and accuracy of just relying on lateral flow tests, scientists have said there are “mountains” of data to show they are excellent at detecting infectious individuals.
Prof McNally said testing negative on a lateral flow and positive on a PCR test happens “because you may have the virus in your body, and your immune system is working against it, and that means you have a tiny amount of virus that can be detected by PCR that’s not enough to be detected by the lateral flow, which means that you’re not infectious”.
“To be infectious you have to be shedding the levels of virus that are detected by the lateral flow device,” he added.
The difference between the lateral flow and the PCR tests, Prof McNally explained, was that the lateral flow “detects the actual virus, that living small thing that attaches to your cells and goes inside and causes the infection”, while the PCR “just looks for the genetic material of the virus and amplifies it to find it, so actually it can find minuscule amounts”.
Scientists agree, however, that exercising caution is still very important to help curb the spread of Covid.
“If the lateral flow test is negative and you have symptoms then you have to be really careful, the lateral flow status can change in a matter of hours, so if you have symptoms that trumps everything and you should stay at home, and you shouldn’t be mixing especially with loved ones and people who may be more clinically vulnerable,” Professor McNally said.
Health experts advise that lateral flow tests should be taken regularly before mixing with others or if you suspect you have symptoms in order to keep the virus at bay.
“I think there are two reasons I would take a lateral flow test; because I was going to mix with people and I wanted to protect them from being infected by me and then if I had any sort of a symptom of any sort of a respiratory infection, so, fever, headache, tiredness, aching limbs, aching bones, a cough, a runny nose.
“In all honesty, given how much access we have to lateral flow tests, any sort of symptom of a cold or a flu, I would be taking a lateral flow test,” Professor McNally advised.