A test to determine whether people have been infected with coronavirus in the past has been approved by health officials and will be rolled out across the country from next week.

Here, we answer the key questions surrounding the new test.

– What is the new test?

Swiss pharmaceutical giant Roche and American rival Abbott Laboratories have each developed a test which can tell whether somebody has ever had the coronavirus.

It involves taking a small sample of blood and testing it for antibodies which will indicate exposure to coronavirus.

Public Health England (PHE) has evaluated the tests and approved them as being safe and reliable for widespread use.

– How reliable is it?

Very. The test picks up 100% of people who have had coronavirus.

This means it has 100% sensitivity.

It also has a specificity of at least 99.8%, meaning there is only very small room for tests to come back as false positive.

– What if I’ve never had any symptoms of Covid-19?

It doesn’t matter.

Experts believe a proportion of people who have had Covid-19 never actually develop symptoms.

The new test can identify people who have had coronavirus even if they have never had any indication they are infected.

– If the test shows I’ve had Covid-19, am I now immune from it?

At present, the science is inconclusive as to whether a positive test result for antibodies means a person is immune to Covid-19, or whether or not they can be re-infected with the virus, or pass it on. Research is ongoing to learn the answers to these questions.

Experts believe that while the presence of antibodies indicates a level of immunity, it is unclear whether people are completely protected and how long any immunity lasts.

There has been some suggestion that immunity could last for two to three years but more work needs to be done.

In the meantime, if someone tests positive, they will still need to follow social distancing measures and appropriate use of personal protective equipment (PPE).

– Who can have the new test?

Ten million tests will be rolled out in a phased manner over the coming months, with England’s health and care staff, patients and care residents first in line.

The Government says it will also arrange supplies of tests on behalf of the devolved nations, who will decide how to use their allocations.

In England, health and social care staff will be asked by their employer whether they want to have an antibody test.

Clinicians will be able to request tests for patients in hospital and in social care settings if they deem it appropriate.

For care staff, the roll out will be phased across regions, with the Government and local leaders to decide the most appropriate places to start.

It is hoped the test will become available to the wider public, although it is unclear how and when this will happen.

In the meantime, people who are having blood tests for other ailments will also be asked if they would like a coronavirus antibody test.

– What is the major benefit of the testing?

Accurate and reliable lab-based antibody tests will improve understanding and data on Covid-19.

If it is eventually proven that people with antibodies are immune, they could safely return to work and socialise with other people without fear of catching or spreading the virus.

The testing will also show how long antibodies stay in a person’s system, which could help in the development of treatments and vaccines.

– How does it work?

A blood sample is processed by centrifuging or spinning it using automated equipment already installed at NHS sites across the UK.

This makes a part of the blood called the serum, which contains antibodies for all sorts of things, rise to the top.

Special chemicals called reagents are then added to it and if Covid-19 antibodies are present, the chemicals trigger a light reaction which a machine detects.

– Is it a potential ‘game changer’ as Boris Johnson has suggested?

If it proved immunity, people could safely go back to work and socialise.

On a large scale, it could also provide essential information for tracking where the disease has been and forecasting future hot spots.