[EXPERT REACTION] Different types of testings for COVID-19

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There has been some questions from journalist about the different types of testing for COVID-19. Here are the expert reactions gathered by SMC UK.


Prof Nicola Stonehouse, Professor in Molecular Virology, University of Leeds, said:

“There are basically two kinds of tests – one evaluated whether you are currently infected and the other evaluates whether you have been.  We need both. For SARS CoV2, the former test detects viral genetic material – RNA.  This is a PCR based test.  The latter detects antibodies to the virus. I think the confusion has arisen from the viral RNA incorrectly being termed ‘antigen’.”

Prof Eleanor Riley, Professor of Immunology and Infectious Disease, University of Edinburgh, said:

“Tests for the virus (current infection) are often called “antigen” tests – where antigen refers to some component of the virus, typically the external (coat) protein of the virus.  However, the test being used for COVID-19 is actually looking for viral RNA (which is technically not a viral antigen).  So when people talk of “antigen” tests and others talk of tests for viral RNA or “PCR tests” they are actually talking about the same thing.  I would prefer if people would simply talk about tests for the presence of the virus – which covers all eventualities – and clearly differentiates it from tests for antibodies (which we don’t have yet).”

Dr Zania Stamataki, Viral Immunologist, University of Birmingham, said:

“There are two types of tests that we carry out for COVID-19, one is to confirm if you currently have the virus (PCR) and one is to ask if you have made antibodies against the virus (serology). Both kinds of tests help us make public health decisions about measures to contain the outbreak.  Information from these tests is important to help us return to work, reopen schools and relax restrictions.

“The PCR test detects the virus, and it is important to determine if someone who is very ill has COVID-19. The test uses swabs from the nose and throat and has a high accuracy rate, but it doesn’t pick up all infections. Some countries test as many people as possible, others test those that develop serious symptoms of the disease. This has to do with logistics, it is very difficult to scale up testing for large proportions of the population.

“PCR testing is important early in infection because it can help us isolate infected people and contain the outbreak. PCR testing is also important later in the outbreak because it shows us how the virus is transmitting through the population and we can then calculate the percentage of people that develop serious complications, which reveals how dangerous this virus is for different people (young and old, men and women, people with other health problems). If we don’t test for the virus, we will be unable to decide if our measures to contain transmission are working. For example, have the school closures made any difference?

“Serology testing reveals if you have been exposed to the virus, and your body has developed antibodies. IgM antibodies are present early in infection, IgG antibodies (seroconversion) arise a few days later. COVID-19 is new for humanity and you will not have antibodies against it if you have not been infected. We don’t know yet if your antibodies are able to protect you against re-infection, and we don’t know how long they will last in your blood. It is likely, however, that if you have recovered, you should be able to return back to work. Some countries like Germany are investigating using serology results as an “immunity passport” to advise those that recovered to return to work.

“Antibodies can reduce infection by blocking virus attachment to target cells (neutralising antibodies). If antibodies are protective, a vaccine will generate immunity to the virus and help us return to normality. There are dangers to antibodies too in COVID-19, and it was reported that antibodies can activate immune cells which leads to collateral damage in the lungs  https://insight.jci.org/articles/view/123158. A study in five critically ill patients that received antibodies from recovered individuals together with anti-inflammatory drugs showed an encouraging reduction in mortality https://jamanetwork.com/journals/jama/fullarticle/2763983.”

These reactions were collected by our sister Science Media Centre (SMC) in the UK. SMC Malaysia is part of a global SMC network which includes countries such as New Zealand, Australia, Germany and Canada working mainly with the national news media and scientists in their respective countries to inject evidence-based information into the headlines.

**All previous posts about COVID-19 here: https://sciencemediacentremalaysia.com/tag/covid-19/

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