Testing has become a controversial topic amid the coronavirus pandemic, as countries, including the UK, struggling to increase figures to match the scale of the outbreak.
When it comes to the actual tests, there are two main types: antibody and antigen. The main, and important, difference between them is that one is useful in determining if someone previously had the infection, and the other is effective in ascertaining if an individual currently has it and is therefore contagious.
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The UK government ordered 3.5 million at home antibody tests last week, with Boris Johnson saying they will be a “game changer”.
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It comes as 38,168 test positive in the UK as of Friday, and 3,605 have died.
The antigen test works by detecting whether the virus is or is not present in the body, while the antibody looks for bodily signs that someone has previously been infected with the virus.
Antibody tests detect the antibodies made even after our bodies have successfully battled a virus, meaning this test is effective in establishing if someone has recovered from Covid-19. If we know someone previously had the virus, they could leave their house without fear of becoming infected.
“This is helpful in telling us whether there is likely to be widespread herd immunity in the population and thus how likely there is to be a second wave of infections (and how big that wave might be) once the social distancing measures are relaxed,” explained Eleanor Riley from University of Edinburgh’s Institute of Immunology and Infection Research.
They work through a blood test that detects two antibodies. The first is short-lived and might highlight that the virus is still present; this antibody only lasts in the body for a few weeks after the illness. The other replaces this one and lasts longer but it is not yet clear how long they can provide immunity to the virus yet.
The antigen tests is usually done using a nasal swab taken from fairly deep into the nose or back of the throat. This kind of testing can highlight if someone currently has the infection and can pass it onto more people.
There are some limitations with the tests however.
“Antigen tests might be falsely negative at the very start of an infection when the viral load is very low, so to be sure a contact of a case is genuinely not infected you would probably need to do a couple of tests two or three days apart,” explained Prof Riley.
On the other hand, “antibody tests indicate that you have been previously infected but don’t guarantee (at an individual level) that you are immune to reinfection”.
Testing in UK
Health Secretary Matt Hancock has set an aim of carrying out 100,000 tests a day in England by the end of April, but the Government is still facing criticism for not doing enough now. He made the announcement on Thursday, adding that this includes both swab and blood tests.
The UK has tested 173,784 people thus far.
Mr Hancock’s plan for improving testing in the country is as follows:
- Scale up swab testing in PHE labs and NHS hospitals for those with a medical need and the most critical workers to 25,000 a day by mid to late April
- Deliver increased commercial swab testing for critical key workers in the NHS, before then expanding to key workers in other sectors
- Develop blood testing to help know if people have the right antibodies and so have high levels of immunity to coronavirus
- Conduct surveillance testing to learn more about the spread of the disease and help develop new tests and treatments; and
- Create a new National Effort for testing, to build a mass-testing capacity at a completely new scale.