It has been described as the ‘best approved test available on the market now’
Public Health England (PHE) has approved a test to find out whether people have been infected with coronavirus in the past.
The antibody test, which Prime Minister Boris Johnson previously described as a “game-changer” – is said to be 100 per cent accurate and could be rolled out within weeks.
However it may be some time before members of the public can get their hands on one.
What is the new test?
The antibody test – the Sars-CoV-2 serology assay – has been developed by Swiss pharmaceutical giant Roche.
PHE has evaluated the test and deemed it to be safe and reliable for widespread use.
It can detect whether someone has had Covid-19 in the past. Given the UK took some time to ramp up its testing of people displaying symptoms of the virus, the antibody test is likely to be in high demand.
It could mark a breakthrough in assessing how widely spread the virus is – and indicate how many people might have immunity.
What does the test involve?
Individuals will give a sample of their blood which will be tested for antibodies. If detected, it will indicate that they were exposed to Covid-19.
The test will even identify people who have had coronavirus but did not display any symptoms at the time.
Taking the human blood sample, lab professionals will separate the red blood cells to obtain the serum, or plasma, through a process known as centrifugation, according to Roche.
Reagents are then added to the serum. If Covid-19 antibodies are present, the chemicals trigger a light reaction which a machine detects.
How accurate is the test?
The test is 100 per cent accurate, meaning it will pick up 100 per cent of people who have had the virus.
It also has a specificity of over 99.8 per cent, so it will pick up virtually all people who have not had coronavirus.
A test that is 100 per cent specific means all healthy individuals are correctly identified as healthy – there are no false positives.
Who can get a test?
Roche says it will be able to provide hundreds of thousands of antibody tests to the UK every single week.
The Government has said the tests will first be rolled out to frontline workers, such as those in health and social care.
After that it may be rolled out more widely but the timeframe remains unclear. It is also not known whether they will be available through the NHS or another website.
Won’t that be too late?
It is thought that antibodies stay in the blood for up to two years, so there is plenty of time for the public to get a test.
Professor Sir John Bell, regius professor of medicine at Oxford University, told Radio 4’s Today programme that antibodies “stick around probably for a year or two”.
He added that the Roche test was the “best approved test available on the market now”.
What does the test mean for immunity?
There are still a number of questions around whether people who have had Covid-19, and who have recovered, are immune.
Although the test is a “very positive development”, Professor John Newton, national coordinator of the UK Coronavirus Testing Programme, said it was still unclear to what extent the presence of antibodies indicated immunity to Covid-19.
Experts have said antibodies suggest a level of immunity, but it remains unclear whether people are completely protected and how long any immunity lasts.
Some have suggested that immunity could last for two to three years but more research is needed.
When more information about immunity is available, the test could be an important tool for lifting the lockdown. People would be able to return to work or socialise, knowing it is unlikely they will get the virus again.