Brits are still being denied private coronavirus antibody tests more than a fortnight after blood samples taken from the finger were temporarily banned by the health watchdog.
The Medicines and Healthcare products Regulatory Agency (MHRA) — a branch of the Department of Health — pulled the home testing kits, which check if someone has previously had the disease, on May 26.
Officials said they were urgently reviewing the accuracy of the devices, which draw blood using a finger pricker and scour the sample for Covid-19 antibodies — even thought they had been on sale for weeks.
But the tests are still listed as ‘out of stock’ at some retailers and online pharmacies, including Superdrug, nearly three weeks later. The MHRA claims it suspended sales of the devices over fears they produce unreliable results.
The Government has only validated two antibody tests, made by pharmaceutical giants Abbott and Roche, which are both designed to use a blood sample from the vein and are processed in a lab.
Private firms jumped on PHE’s approval of those testing processes earlier this month to start selling their own tests. Confusingly, the lab-based equipment used to process the tests is the same as for the national scheme.
But the companies that make the equipment insist they are not designed for finger-prick samples. The MHRA ban only concerns tests which rely on people taking their own blood from their finger, not ones which use professional samples of vein blood.
Regulators today told MailOnline the services won’t resume until the manufacturers of the kits begin to test whether they work for finger-prick samples themselves. The MHRA said it does not ‘have any timescale for when any such testing service may be available’.
It comes after it was revealed patients wanting antibody tests to tell them whether they have had coronavirus could be turned down by their GPs, who have been told they are under no obligation to offer the tests.
Ministers purchased 10million of the kits in late May and has been using them on NHS and care home staff ever since.
NHS England recommended GPs offer the tests to patients who are having bloods taken for other reasons, if the patient wished to know if they had the virus.
But BMA GP Committee chair Dr Richard Vautrey warned that family doctors should be wary of giving out too many of the kits.
He told Pulse Magazine: ‘There is no clinical benefit of just having an antibody test and we wouldn’t want to see that driving up inappropriate attendance in GP surgeries.
‘We need to really understand much more about the long-term benefits of having antibody tests other than it being a surveillance tool for public health purposes.’
The MHRA wants to ensure that blood taken from a capillary (a home finger-prick sample) shows the same levels of accuracy as blood taken from a vein.
The best-known company providing antibody tests, Superdrug, says on its website it has ‘temporarily halted the Covid-19 antibody testing service’.
Although the £69 test has been part-approved by Public Health England, Superdrug was asking people to take their own blood samples, which PHE has not approved.
Lloyd Pharmacy’s £59 blood sampling kit – which also used a finger pricker – simply says the device is ‘out of stock’.
An update on Babylon Health’s website says: ‘The MHRA has asked that all COVID-19 antibody testing from finger-prick blood samples be paused. The MHRA decision has impacted all testing of this type nationwide.’
An MHRA spokesperson said: ‘For these services to resume, validation work will need to be undertaken by the manufacturers of CE marked test kits and CE marked sample collection kits.
‘These are commercial decisions made by independent organisations and not overseen by MHRA; we do not therefore have any timescale for when any such testing service may be available.
‘No COVID-19 antibody self-testing kits have received CE mark status and there are no testing kits available in the UK for home self-test use.’
Karol Sikora, professor of medicine at the University of Buckingham, told MailOnline: ‘The Government got our hopes up about these antibody tests in March, but the politicians didn’t really understand them.
‘They thought they would be much more accurate and that their would be a higher percentage of the population who had been infected.
‘It’s a good thing they’ve been removed [from supermarket shelves] and the UK should just use them in surveillance studies moving on.
‘People shouldn’t worry about not being able to get the private tests – some of them are a rip off and they don’t really tell you anything. It’s not like you get some kind of immune privilege if you get a positive result.’
The way current antibody tests work is that someone takes their own blood sample, or a medical professional takes it for them, and that is posted off to a lab.
There, qualified technicians analyse the blood to look for antibodies for the coronavirus, which are immune system substances created when someone is infected with the virus.
People then receive a result in which the presence of antibodies – a positive result – indicates they have already had the virus, or the absence that they have not.
Antibody testing has been ongoing throughout the pandemic and more than 230,000 people have been tested in a bid to try and work out what proportion of the population has had the virus.
Health Secretary Matt Hancock said almost one in five people in London – 17 per cent – have already had the coronavirus, according to surveillance testing.
Meanwhile the rate across the rest of the UK appeared to be around five per cent, he said, which would equal 2.85million people.
But only two tests – ones made by Roche and Abbott – have so far been considered good enough to diagnose people on an individual basis – to tell them the results.
Antibody studies, also known as seroprevalence research, are considered critical to understanding where an outbreak is spreading and can help guide decisions on restrictions needed to contain it.
There is currently a high level of inaccuracy in the testing, however, caused by how uncommon the virus is within the population.
If the infection has affected only a small number of people tested, it will have a magnified margin of error.
The way this maths works is that a 95 per cent specific test, for example, will always produce five false positive results from a group of 100 people.
Even if it is sensitive enough to detect all the people who have genuinely had the disease, it will still return five false positives.
If the prevalence of antibodies is low – for example, only five per cent of people in the group have had the illness – the results could end up half wrong. The 95 per cent test, in that situation, would be expected to return 10 positives – five of them right, five of them wrong.
This means the functional accuracy of the test is only around 50 per cent.
This effect is magnified if the prevalence of the virus in the population is low, and less noticeable if the prevalence is high.
For example, if 30 per cent of the population have been infected, those five false positive results would be counter-balanced by 30 true positives in the 100.
A more specific test can reduce this effect; by comparison a 99.9 per cent specific test would return one wrong result per thousand – 100 per million.