As the pandemic has progressed, there has been growing public interest in the potentials of testing. With reliable means of detecting whether someone has or has had the virus, we might better adjust not only public policy but our own lives, which have been so abruptly interrupted. There has been endless discussion about the possibilities of immunity for those who have contracted the virus and survived. There have also been doubts about the reliability of rapid testing, which remains the most convenient form of testing for the general public – and for business owners.
Indeed, for many small businesses, the answers to these questions will be pivotal. However, answering these questions requires at least a minimal knowledge of viral testing and there has been a pitiful lack of accessible information. As part of our campaign to empower small businesses during the pandemic, we thought it might be useful to produce this short and simple introduction to viral testing.
Let’s start with the absolute basics. A virus is parasitic, meaning it cannot survive without a host. Its host is a cell. A virus is chiefly composed of two elements: a nucleic acid molecule and a protein shell. ‘Nucleic acid’ might sound familiar to you, a distant memory from a school classroom where you were given a lecture on DNA – the ‘secret ingredient of life’. It is this element of a virus that is responsible for the replication which can make them so dangerous.
In order for a virus to replicate, though, it must attach itself to a cell – its host. This is where the protein shell comes in. Think about all of those images of the COVID-19 virus that you will have seen on the news or in articles or on the government’s public safety posters that are now dotted all over the place. The virus has a bunch of ‘spikes’ sticking out of it, right? Well, these are part of the protein shell and they’re the virus’ way of gaining access to a cell.
They are also what attracts the attention of the body’s immune system. When the body produces antibodies against a virus, it is these protein ‘spikes’ which they are designed to hunt out. This brings us to the first of the two major forms of COVID-19 tests: the antibody test. In an antibody test – like our rapid antibody test -, the filter paper onto which the blood-sample is placed already contains proteins extracted from the COVID-19 virus. If you have the relevant antibodies in your blood, they will react with the proteins on the paper, producing the marks that can be seen on this test from one of our customers:
Antibody tests have come under fire in the past few months for a number of reasons. (We have a whole blog on the topic, if you’re interested.) But the main concerns revolved around the sensitivity of the tests. Firstly, it takes a while for detectable levels of antibodies to be produced, meaning that antibody tests do not give us a totally comprehensive picture of who currently has the virus. Similarly, in the other direction, it is hard to pinpoint exactly when the levels of antibodies cease to be detectable and whether this has any bearing on immunity, for example. Take a look at this diagram:
However, the picture used above is of a test taken by one of our customers, whose husband had symptoms over 60 days ago, which means that antibody testing might be reliable far beyond the limit previously assumed.
So, what is different about an antigen test? Instead of testing for antibodies which fight the virus, antigen tests are able to detect the genetic material of the virus, that nucleic acid we discussed earlier. Because this genetic material is present as soon as someone is infected, antigen tests offer a more comprehensive picture of who currently has the virus than do antibody tests. However, antigen tests cannot give us information on who has had the virus in the past, which is the added benefit of antibody tests. Such a hard limit to the testing window is reflected in the NHS’ guidance on getting one of their antigen tests:
We hope that this information clears up a few misconceptions about testing and gives you the confidence to lead your business through the current challenges. For more information, and to view our range of health and safety products, check out our website.