What is the test that Public Health England (PHE) has approved?
It is a lab-based test for antibodies in the blood of people who have had Covid-19 and recovered. It is made by the giant pharmaceutical and diagnostics Swiss company Roche, which calls it the Elecsys® Anti-Sars-CoV-2 antibody test.
How does it work?
A healthcare professional in a clinic or hospital will take a blood sample from the person thought to have had Covid-19. That has to be done no earlier than 14 days after their symptoms began, to allow time for the immune system to mount an antibody response to the virus. The sample is then dispatched to a lab that has the analyser machines needed to process it. Roche says its automated systems can provide results in about 18 minutes for one single test, with a capability to do 300 tests an hour, depending on the analyser.
Is it the rapid finger-prick test that PHE was hoping for, that can be used at home?
No. The test must be analysed on big, expensive machines that hospital laboratories already have for running other Roche tests for different conditions. A lot of finger-prick home tests have appeared on the market and are available to buy online. Oxford University has assessed many of them – and it still assessing others – but has rejected all of them as not sufficiently accurate. Unlike those, this test has been validated by PHE’s labs at Porton Down.
Is the Roche test a breakthrough that will allow everybody who has had Covid-19 to have an immunity passport and get back to their old lives?
No. There are very big questions still over the implications of a positive result. If there are antibodies in your blood, it certainly means you have had Covid-19, and you may be immune to getting it again. But nobody knows what level of immunity is conferred, whether some people have an antibody response that gives them greater immunity than other people and how long that immunity lasts.
Offering people immunity passports is clearly risky anyway, because they could be forged or people could deliberately adopt risky behaviour in the hope of getting infected and being released from lockdown.
What is the use of the test then?
Antibody tests like this one will help find out what proportion of the population has had Covid-19 and an understanding of how it has spread. So far, studies in other countries suggest prevalence is low – under 10%.
That knowledge would potentially allow different strategies to be adopted in different areas – for instance, if there were high levels of antibodies in a community, there might be a level of herd immunity that would allow more shops such as hairdressers to open, although still with precautions to avoid infection.
Will it definitely be adopted by the NHS?
We don’t yet know but it is very likely. The Roche test is being bought in bulk by many other countries since it was approved by the US and the EU authorities at the beginning of May. The test has been certified by those authorities and now approved by PHE as virtually 100% specific and sensitive. Edward Argar, the health minister, said on Thursday no tests had been purchased by the UK as the government was still in discussions with Roche about acquiring them.
