Coronavirus antibody test: what is it and what does it mean for COVID-19?

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A ‘highly specific’ COVID-19 antibody test has been approved by Public Health England.

Medically reviewed by Dr Roger Henderson and words by Jessica Rapana

As the UK government begins the easing of lockdown measures put in place to stop the spread of coronavirus, it is now looking to antibody testing, which could help to determine who has had COVID-19 and therefore might have some immunity to the virus.

But what is an antibody test and how do they work? Here is what you need to know.

What is an antibody test?

Antibody tests, also known as serological tests, show if you had a previous infection with a virus by looking for antibodies in your blood. Antibodies are proteins that help fight off infections. People who have had COVID-19, including those who were sick without symptoms and those who were sick and have recovered, will possess these antibodies.

Can an antibody test detect a current infection?

Antibody tests are not intended to detect a current COVID-19 infection as it can take 10 days or more for coronavirus antibodies to become detectable in a person’s blood after recovery.

Why are antibody tests helpful?

Accurate testing for the virus and the prevalence of antibodies will provide the government with a clearer picture of the spread of the disease and how many have been infected.

These tests will also shed more light on those individuals who may have had some immunity to the virus and help the government to plan services for those who do not.

“Understanding more about the current spread of coronavirus and the prevalence of antibodies is a vital part of our ongoing response to the pandemic,” health minister James Bethell said. “This information will inform the future action we take to manage the spread of the virus, including the development of new tests and treatments.”

Will I be able to get an ‘immunity passport’?

The idea of a so-called ‘immunity passport’ or ‘risk-free certificate’ that would enable individuals to travel or return to work assuming that they are protected against reinfection has been floated in some countries as a way of easing lockdowns.

However, the World Health Organisation (WHO) has warned that this could lead to an increase in virus transmission because there was “not enough evidence” that people who developed antibodies after recovering from the coronavirus were protected against reinfection.

Do coronavirus antibodies confer immunity?

Not necessarily. While the presence of coronavirus antibodies indicates that a person has had COVID-19, it does not guarantee that a person cannot be reinfected with the virus. Even if these antibodies do confer immunity, researchers still don’t know how long this protection will last.

Certain virus antibodies provide lifetime protection from infections, such as smallpox, while others tend to fade over time. On April 24, the WHO announced that “no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans”.

How accurate are coronavirus antibody home tests?

No home antibody test has yet been proved to be reliable enough to be used.

A preliminary study, published this month, found that of the 14 coronavirus antibody tests available in the US only three delivered consistently accurate results. The others produced false positive results between 5 per cent to 16 per cent of the time.

The UK government previously raised the idea of making antibody home-test kits available to the public to buy from Amazon and Boots. However, it backed away from the idea after the 3.5 million commercial finger prick tests it ordered were not good enough to use.

Who can get a coronavirus antibody test in the UK?

The government has set out a two-part testing programme for coronavirus. The first part of the programme, which is already underway, involves testing 100,000 randomly selected people across England to see whether someone is currently infected with the coronavirus. Their nose and throat swabs will be tested for antigens, which indicate the presence of COVID-19. Antigens are structures within a virus that trigger the immune system’s response to fight off the infection and can be detected in a person’s blood before antibodies are made.

In the second part of the programme, a number of different antibody kits will be tested for accuracy and their ease of use at home. The antibody tests will be first carried out on volunteers from Imperial Healthcare NHS Trust, who are known to have had the virus, to assess their accuracy. The test will also be given to 300 public volunteers to self-administer, which requires them to place a finger prick of blood in a cassette, add a dye and read off the result.

If the tests are shown to be accurate and easily usable, the test will be distributed to up to more people with the potential to be rolled out to 100,000 people later this year in order to provide an indication of the prevalence of COVID-19 based on the presence of coronavirus antibodies.

When will we have an antibody test in the UK?

Public Health England has now approved a new antibody test, developed by Swiss pharmaceutical company Roche, to find out whether people have been infected with coronavirus in the past, the BBC reports.

The blood test looks for antibodies to detect whether a person has already had COVID-19 and might now have some immunity. The test, which has already been approved by medical regulators in the EU and the United States, was found to be “highly specific” when evaluated by experts in the UK last week, Public Health England said.

Roche is understood to be talking to the Department of Health and Social Care about possible use by the NHS. The tests will primarily be used on those in the NHS and social care to begin with, health minister Edward Argar told the BBC. However, there has been no indication of when such testing could start.

Net Doctor

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