Coronavirus: Antibody test could ramp up Covid-19 screening, say Cambridge biotechnology experts
A new COVID-19 test is on the way and, subject to regulations and availability, could soon be used to test millions of people.
Until now, the preferred testing in the UK and in the world - as recommended by WHO - for coronavirus infection has been molecular diagnosis using RT-PCR (reverse-transcriptase polymerase chain reaction). This test detects the presence of genetic sequences of the virus in the person. For this it requires a swab from the throat or nose, with the sample sent off to a laboratory for further processing - which involves amplification of tiny traces of the virus if present - and analysis. However, some NHS trusts say they can only carry out a limited number of tests because of shortages of swabs, testing kits and reagents.
The news of a new rapid test was announced yesterday. The SAMBA II test fully automates the process and will be used in some hospitals, with Addenbrooke’s among the first. These tests are molecular diagnostic, which has been the preferred testing technique used in labs for 30 years.
The third test has emerged because, despite the high need for Covid-19 testing, there is a shortage of reagents, creating a market for a non-PCR option - such as the antibody test. Checks for antibodies are potentially as straightforward as a pregnancy test. The antibody route could help ramp up testing, as it doesn’t require the reagents which are in short supply.
Awareness of antibody tests is advocated by Dr Jessica Ocampos, founder of Camnexus, a technology transfer platform for sustainable development based in Cambridge, and Dr Mengmeng Wang - both have PhDs in chemical engineering from the University of Cambridge and are specialists on biotechnological enterprises.
“PCR tests require people with training to take and test a sample,” Dr Ocampos told the Cambridge Independent. “The test involves very tiny pieces of material which have to be amplified, and that takes time. The shortage of reagents means that the number of tests you can perform has decreased. This shortage of diagnostics means we can’t screen as many people as we want and more people are getting sick.
“So researchers are looking for other ways to do the screening.”
Serological, or antibody, tests offer such an alternative. Instead of detecting the virus, an antibody test searches for the body’s response to the virus. Using a blood sample, the test detects if a response to the virus is present. This immunoassay procedure involves mixing a blood sample from a pinprick on the skin with a strip of paper containing antigens: depending on the colour the paper turns to, the person either has or does not have the coronavirus.
“The PCR is a molecular test using RNA, but the use of immunoassays, where you take a sample of blood, is super-good as it is very fast,” says Dr Ocampos. “You take a sample of blood under trained supervision to see if there’s antibodies in the blood, and you put concentrations of antigen on a strip of paper. When they recognise the antigen they produce a colour change, like a pregnancy test.”
The big advantage of these tests is that they can detect if someone has been infected even if they have recovered. The UK government has included antibody tests to meet the target it set this week of 100,000 tests a day by the end of April.
Indeed the only obstacle to the wholesale introduction of the antibody test is the antigen, which is extracted from a sample of the virus.
“You need access to the antigen of the virus,” Dr Ocampos adds. “That’s why not many nations can develop these tests. At some point all countries will have the capability - here at Addenbrooke’s, for example, it will be okay if you have access to the virus. It’s very important for the next wave of scientific knowledge - the first wave was in China, and then the virus spread round the world and hopefully more centres will have access to the tests.”
The Chinese are ahead of the curve in this respect.
“In China they’re already doing the tests,” says Dr Ocampos. “There are eight manufacturers of serological tests approved by China. There are no other approved tests in that area.”
The race is on and indeed an antibody test is now under way at the all-important FDA - Food and Drug Administration - in the US. In the UK, Bedford-based Mologic has begun a validation process for a Covid-19 point-of-need test.
But Dr Ocampos is also keen to point out the dangers.
“We need to be really careful with the information because I have seen many websites with people claiming they have these rapid tests. As a consumer you need to look at the certification - the CE mark - and moreover if the tests have been approved by either the FDA or its regulatory equivalent in each country.”
Regulatory approval in the UK is currently in a transition - due to end on December 31 - following the 2016 referendum which resulted in the UK signing off from the European Medicines Agency, which relocated from London to Amsterdam last year.
The wider problem is that some companies from China have claimed they have approved tests when in fact the devices involved have not been approved. This is discussed by Dr Ocampos and co-author Dr Mengmeng Wang - both studied chemical engineering at the university 2011-2015 - who described in a recent post on LinkedIn titled ‘We Need to Ensure World Governments and Leading Organisations are Purchasing Certified COVID-19 Rapid Testing Kits’.
“While those Chinese manufacturers claiming to supply testing kits may have a CE mark, allowing them to import and sell their products in Europe, this does not necessarily mean that they have clinical trial data behind them; rather, this would require them to have FDA or NMPA approval,” she writes.
The concerns over Chinese-exported coronavirus medical equipment have extended beyond testing. The Netherlands recently took delivery of 600,000 defective masks, the BBC has reported.
Meanwhile manufacturers are waiting on regulatory approval for the antibody tests before they can be rolled out.
Last week Matt Hancock, UK health secretary, announced that the country had ordered 3.5million antibody test kits from various manufacturers. The regulatory approval is worth waiting for - to ensure only fully tested and compliant tests are being imported from China. To that end, it may be that UK-based Chinese agencies will assist in ensuring that the UK government’s procurement procedures are robust enough to withstand any non-approved healthcare equipment coming our way any time soon.
More by this authorMike Scialom