Last updated: 16 July 2020
As coronavirus testing becomes more widespread in the UK, find out what you need to know about the different types of test, how to get one, and why not to spend money on pricey private tests.
Anyone in the UK displaying symptoms can now apply for an antigen test – to tell you whether you currently have COVID-19.
Meanwhile, antibody tests – which tell you if you’ve previously had COVID-19 – are available to the general public, but only if you have blood taken by a healthcare professional. We don’t think they’re currently worth buying as they are expensive, and there are important limitations on what they can actually tell you.
Antibody tests where you take your own blood sample with a home fingerprick test have been taken off the market while this sampling process is investigated by the Medicines and Healthcare Products Regulatory Agency (MHRA).
It’s important to know the difference between the two tests, what’s available and what’s legitimate, as well as the limitations of antibody testing.
Read on to see all the latest advice, or use the links below to skip to certain sections:
Coronavirus news and advice from Which? – head to our hub for all the latest advice from our experts.
COVID-19 testing explained
This swab test, taken from inside the nose or mouth, already exists and indicates whether a person is currently infected with the disease. This type of test takes longer to process as the samples need to be analysed in a lab.
The government is now encouraging everyone with symptoms to get a coronavirus antigen test as part of the NHS Test and Trace program (see below).
You can request this swab test online, and it can be done at a drive-through testing centre, at a mobile testing unit, or via a home test kit. It tells you whether you’re currently infected with COVID-19. It involves swabbing the inside of your nose and the back of your throat, using a long cotton bud.
You have to administer the test yourself and it can be very unpleasant as the swab needs to go quite deep. 41% of Which? members who had taken this test said they found it difficult to do and patients have told us it can be easy get wrong, especially when you’re feeling unwell.
Testing at hospital is available for patients and some NHS workers.
The government website urges people to request a test as soon as they develop symptoms, and says testing must be done within the first five days of having symptoms. You can book a test online through the NHS.
Randox test kits recalled
Some test kits used by the NHS for Coronavirus swab testing have been recalled due to concerns they do not meet safety requirements.
The government has asked that the use of test kits manufactured by Randox Industries is paused while the issues are investigated.
Randox tests carried a CE mark but concerns were raised when certification for the kits wasn’t forthcoming, Health Secretary Matt Hancock said.
The government stressed that the risk to safety is low and that there is no evidence of harm done.
This only applies to unused test kits manufactured by Randox Industries. All other kits being used by NHS Test and Trace can continue to be used.
Used Randox tests can still be processed, and test results from Randox kits are not affected.
Matt Hancock said that there will be no impact on access to testing.
Understanding swab test results
Some doctors have raised concerns about the false negative rate for coronavirus antigen testing, leading to possible false reassurance.
It is not known what the rate of false negatives is (a report in the British Medical Journal estimated it is between 2% and 29%), but a negative result from a swab test is conveyed to patients in very definitive terms – ‘you did not have the virus when the test was done’ – without any information about what might affect the result or its accuracy.
The government advice does tell people to continue isolating if you’re feeling unwell, even with a negative test result.
There are also worries about the lack of information about an inconclusive test result, with patients simply being told their test is unclear and to consider applying for another one, but no information as to why this might be or how to avoid invalidating the test on another try.
How does NHS Test and Trace work?
The steps for NHS Test and Trace are:
- Isolate – as soon as you have symptoms and for at least 7 days, while anyone you live with must isolate for 14 days from the onset of your symptoms
- Test – request a test as soon as possible
- Result – a positive result means you continue to isolate for the time set out above, if it’s negative you and anyone you live with can stop isolating
- Share contacts – the government website explains that ‘the NHS test and trace service will send you a text or email alert or call you with instructions of how to share details of people with whom you have had close, recent contact and places you have visited.’
Read our advice on how to tell if an NHS test and trace message is a scam (this advice refers to Public Health England so applies to people in England).
An NHS contact tracing smartphone app was supposed to form part of this system, but hasn’t gone to plan. The app was being trailed on the Isle of Wight but problems with the way it worked (including that it didn’t detect iPhones properly) meant plans were scrapped in favour of a different version which is being developed with Apple and Google. It is not known when the new app will be available, with some estimates saying winter.
Find out more about how NHS test and trace works on the government website.
This blood test should show whether a person has already been infected by detecting the presence of the antibodies our bodies produce to kill the virus.
Health officials in England have approved an antibody test, manufactured by Swiss company Roche. The test has previously been approved by the FDA in the US and by some European health regulators.
It is not yet available to the general public in the UK, but is beginning to be rolled out to health and social care staff, patients and care home residents. Health Secretary Matt Hancock said that each devolved nation is deciding how to use its test allocation and how testing will be prioritized and managed locally.
The antibody test needs to be analysed at a laboratory or hospital with the appropriate equipment. It has been shown to be highly accurate, and is therefore the first approved antibody test that can reliably identify if somebody has had COVID-19.
This is an important step as it increases potential for wider testing and identifying the spread of the disease. Expanding accurate antibody testing would help experts understand how far the virus has spread, and how many people might have had it asymptomatically, or with mild symptoms.
Antibody tests are measured on specificity – which measures the proportion of ‘true’ negatives – and sensitivity, which measures the proportion of ‘true’ positives. The Roche test, analysed using a machine already widely available in hospitals and labs, was said to have greater than 99.8% specificity and 100% sensitivity.
However, a subsequent PHE evaluation found a sensitivity rate of just 84% for the same test. Multiple antibody tests are still being evaluated.
How accurate are antibody tests?
Jon Deeks, Professor of Biostatistics at the University of Birmingham, says that while a positive result is fairly definitive, a negative result is less certain.
Professor Deeks explains that antibodies might not present as strongly in people with mild or no symptoms and studies so far have mostly been done on patients with severe cases – so this could skew the data for how accurate the tests are.
Different types of antibody test
The officially approved antibody test is not yet available to the public. The process is different from the commercial tests as it uses a blood sample taken from a vein, and must be administered by a healthcare professional in a clinical setting.
No home test kits for COVID-19 where you conduct the test and instantly get a result at home can legally be sold int the UK, so you should be cautious of any company claiming to sell them. Validation tests on this type of home test kit revealed that they weren’t very accurate, so the ones bought by the government were abandoned.
The General Pharmaceutical Council has said rapid result antibody tests should not be conducted in pharmacies either, and has asked pharmacies providing these types of test to stop doing so.
The Medicines and Healthcare products Regulatory Agency (MHRA) has raised concerns that the confusion around the availability of testing kits could also fuel the marketing of fraudulent test kits by scammers.
Still plenty of unknowns around COVID-19 immunity
It is hoped that once someone has had COVID-19, they are immune to the disease, but crucially, this is still uncertain.
The presence of antibodies in your blood can tell you you’ve been exposed to the virus, and therefore can also offer some information about how you reacted to it, but at the moment that’s about it.
The WHO says that ‘we expect that most people who are infected with COVID-19 will develop an antibody response that will provide some level of protection. What we don’t know yet is the level of protection or how long it will last.’
It warned against making assumptions about a person’s immunity to COVID-19 based on antibody testing. A positive result shouldn’t yet be interpreted as a stamp of immunity.
Moreover, any level of immunity can only be assumed in the short term because we just don’t have long term data yet on how this virus behaves.
Professor Deeks says ’we don’t know how long antibodies last, and we don’t know how effective they are at fighting disease.’
Can you get an antibody test?
We’ve previously advised caution about spending money on an at-home COVID-19 antibody test, as there could be a risk that they encourage a false sense of security with a positive result.
Some private companies are now offering to send a healthcare worker to your house to administer the test by taking blood from a vein, or selling tests with a clinic visit included. This generally costs about £100-£130 per test.
Home antibody tests that you do yourself with a finger-prick blood sample have been taken off sale while the methodology they use is investigated.
Companies supplying these tests – which included Superdrug – have been asked by the MHRA to stop selling them for now, and not provide customers with results until a review of the process has been undertaken.
These tests require you to take a blood sample by pricking your fingertip, and sending it off in a vial to be analysed by a lab. What the MHRA is looking into is the process of taking a blood sample from your fingertip at home, and whether samples collected in this way will yield accurate results.
The MHRA says that antibody tests ‘should only be performed and interpreted by fully trained, healthcare professionals and not by members of the public.’
So some private companies liked Qured, Medichecks and Forth are offering to send a healthcare worker to your house to administer the test by taking blood from a vein.
Sarah Bolt, CEO of Forth, told us the test would help remove a level of uncertainty as to whether you’d had the virus or not.
She said: ‘at this stage, it is not yet known the depth and length of immunity these antibodies provide, as the virus is relatively new. We hope that it is similar to other viral infections in providing lasting protection.’
Qured told us, ‘the Qured test is being purchased by individuals and employers who want to understand whether they or their workforce have been exposed to the virus and had a detectable immune response.’
It’s important to note that you should continue to follow government advice regardless of an antibody test result. With all the unknowns about the accuracy of these tests and what a result might mean, we don’t think it’s currently worth the money.
For now, the best thing you can do is follow the social distancing guidelines and guidance on how to protect yourself and others.