People must be told the truth about the efficacy of Covid-19 tests, an expert has said.
Jon Deeks, professor of biostatistics at the University of Birmingham, said people should not be told that lateral flow tests are “better than they are”.
The lead researcher of the Cochrane Review of Covid-19 diagnostic tests called for the Government to highlight the message that a negative test does not exclude disease.
It came as an article published in The BMJ called for the Government to rethink the rollout of the lateral flow tests.
He said messaging which suggests that lateral flow tests are as good as PCR assessments is “completely incorrect”.
And remarks that the tests could make workplaces “completely safe” are not the right way to properly inform the public about their efficacy.
There are two main types of test being used in Britain to detect cases of Covid-19.
PCR tests are swab tests of the nose and throat, which are assessed in a lab setting.
Lateral flow tests are quick turnaround tests, which can be performed without the need for laboratory assessment. These are now regularly used by NHS staff and were the main method of testing during the mass pilot scheme in Liverpool.
Prof Deeks told Sky news that the lateral flow tests in Liverpool “missed 60% of the cases which would have been picked up by PCR”.
He said the “false negatives” are a big concern.
“Government messaging on this hasn’t been explaining this to people and it’s a bit difficult,” he said.
We would expect a positive to mean 'yes' and a negative to mean 'no', but here a positive means 'probably' and a negative means 'we really can't tell'Professor Jon Deeks, University of Birmingham
“Most of us have never done a diagnostic test in our lives ourselves, and we would expect a positive to mean ‘yes’ and a negative to mean ‘no’.
“But here a positive means ‘probably’ and a negative means ‘we really can’t tell’.
“So it’s a difficult message to get out to people, and I don’t think it’s been done at all well.”
He added: “Just before Christmas schools were given a template letter, which had the wording in it, and it went to parents saying ‘This test is as good at detecting cases as the PCR’.
“Now, frankly, that is completely incorrect, and that is the sort of wrong messaging which we have to make sure the Government doesn’t continue to put forward.
“This weekend the Business Minister was quoted as saying ‘This will make workplaces completely safe’. It’s not the right way to tell people about this.”
Prof Deeks continued: “I think there’s an anxiety that, if we tell people the truth as to how bad this test is, people won’t bother getting it.
“But we have to do the truth – we can’t tell people that the test is better than it is.”
Meanwhile, a blog published in The BMJ calls for the Government to rethink the rollout of the tests.
"We call on the government to pause the rollout of rapid asymptomatic testing using the Innova test until clearer messaging on the risks of negative results can be developed" @deeksj @DrMikeWGill @angelaraffle https://t.co/W8070LoDef— The BMJ (@bmj_latest) January 12, 2021
The article, published in the journal by Prof Deeks and colleagues, says extending the programme – which could potentially involve at home use – could cause “serious harm”.
“We call on the Government urgently to change course,” the authors write.
They add: “Low test accuracy would be less dangerous if people being tested and the public at large received accurate information about the risks and implications of a false negative result.
“Instead they are being misled.”
They conclude: “We call on the Government to at least to pause the rollout of rapid asymptomatic testing using the Innova test, including its use in care homes, schools, communities and self-testing by untrained people at home, until clearer messaging on the risks of negative results can be developed.”
A Department of Health and Social Care spokesperson said: “Lateral flow devices (LFDs) used by the UK government go through a rigorous evaluation by the country’s leading scientists.
“With up to a third of individuals not displaying symptoms, broadening asymptomatic testing is essential. LFDs detect cases with high levels of virus, making them effective in finding individuals who are the most likely to transmit the disease, including those not showing symptoms.
“14,800 Covid-19 carriers have already been detected using LFDs who would have otherwise not been identified. These individuals have subsequently been told to self-isolate, therefore preventing the onward transmission of the disease.
“Every positive case detected and told to self-isolate is another transmission chain broken, helping stop the spread of the virus.”