EXPERTS have called for a new self isolation rule and tougher measures in schools amid a mystery testing probe.
People have been testing positive for Covid on home lateral flow tests, but negative on the so-called “gold standard” PCR tests.
The problem is focused in the South West area of England, but anecdotal reports have come from across the nation.
Health chiefs at the UK Health and Security Agency (UKHSA) are still investigating the issue, causing mass confusion.
But for now, the official advice stays the same – if a PCR test is negative, you are presumed Covid-free and can leave self isolation.
It has evoked fear that people legitimately carrying the coronavirus are spreading it in schools, offices and elsewhere.
People have been warned to self isolate even if their PCR test is negative, despite Government guidance not doing so.
Dr Kit Yates, a senior lecturer at the Department for Mathematical Sciences at the University of Bath, was the first to point out the growing problem, which began in September.
Asked if it risked public health, he told Trending In The News: “Absolutely I think there is a risk to both public health and our school children.
“We should be protecting our children, but instead it feels like we are abandoning them.
“The one line of defence our kids have is making sure people who are infected are isolating and not actively bringing Covid into the classroom.
“If pupils are coming into school infected then clearly this puts everyone in that setting at greater risk of getting Covid. The same goes for people going into work believing they don’t have Covid.
“They are potentially increasing the risk to their colleagues and allowing Covid to spread further.
“We should be encouraging everyone who can work from home still to do so and we should absolutely be reintroducing mitigations in school like mask wearing, in order to curb the spread.”
Dr Yates added: “Public Health England did issue informal advice which suggested people should isolate if they can after a positive lateral flow test, although this is not official government guidance.
“I think that, where possible, this is what people should be doing.”
But he admitted it may be hard for people to access financial support during self isolation, or sick leave, without a positive PCR.
Prof Christina Pagel, a mathematician and professor of operational research at University College London, said people should “definitely” be self isolating if their home kit gives a positive result.
“Especially at the high case rates we see now,” she told Trending In The News.
“And if you have symptoms AND test positive on LFD [lateral flow] then you should assume you have Covid regardless of PCR test.”
Professor Lawrence Young, a virologist at University of Warwick, also said: “It remains important that if you have symptoms of a respiratory infection and a positive LFT result you behave as if you have Covid-19 irrespective of the PCR result until we know what’s going on with this discrepancy.”
Lateral flows have been shown to occasionally wrongly tell infected people they are Covid- negative, called a “false negative” – although a study today showed they are more accurate than first thought.
However, it’s very rare for it to produce an inaccurate positive result – called a “false positive”.
This suggests the lateral flow tests are almost always correct when they give a positive result, as Dr Yates said: “If you get a positive result on a lateral flow test the overwhelming likelihood is that you have Covid.”
Potential causes
Some suggested the lateral flow tests were confusing another type of common winter bug for the coronavirus.
Prof Young said this was “very unlikely”.
He continued: “This is very puzzling given the high level of specificity of lateral flow tests.
“This leaves several other possibilities including a problem with a specific batch of lateral flow tests or something wrong with PCR testing which could be due to sampling errors (swabbing), processing/testing issues or inaccuracies in recording/reporting results.”
There have been fears of a new Covid variant that is able to dodge PCR tests if it’s mutations remove a gene that the test looks for.
While UKHSA said it was looking into this as a possibility, it said so far there was “no evidence” this was the case.
Denis Kinane, an immunologist and founder of PCR testing co. ExpressTest, claimed there is “no problem at all” with the PCR tests, and in his opinion, people should continue to rely on those results first.
He said: “We have done about two million PCRs and hundreds of thousands of lateral flows, we know exactly what to expect. PCR is the gold standard, no doubt about it.
“It’s very simple to actually make a lateral flow positive, school children have worked that out. You can do that via soft drinks etc. and you can actually change the antibody configuration to some extent, so much so that your lateral flow will come out positive
“I think you should trust the PCR. This winter we’ll see a lot of people with flu coming through, these people will have many of the symptoms of Covid as you would imagine but these people once they are tested with PCR and verified as being negative then, once they’re feeling better, can return to work and be presumed that they had the flu.
“At the moment if you’re positive with a lateral flow and are tested with a PCR then you should trust the tests”.
The NHS website says those with a positive lateral flow test result should “self isolate straight away” and “get a PCR test to confirm your result”.
It adds: “Continue to self-isolate until you get the result of the PCR test. Follow the advice you’re given when you get the result.”
Susan Hopkins, chief medical adviser at the UKHSA, said: ““If you get a positive LFD test, it’s important to make sure that you then get a follow-up PCR test to confirm you have Covid-19.
“If you have symptoms of Covid-19, self-isolate and take a PCR test.”
However, she did not say whether you should self isolate with a positive lateral flow, and negative PCR.
She added: “With any test, it is important to carefully read and follow the instructions for use on the test kit so as to avoid any incorrect readings.”
