COVID-19 ∙ 5 minutes read

Coronavirus test kits explained

By Numan Clinical Team

Testing is likely to play a crucial part in the fight against the new coronavirus. It has already been suggested that the reason why Germany has such a low virus fatality rate is because it performs 160,000 tests a week — more than some European countries have performed since the outbreak started. 

Now, the development of coronavirus test kits is accelerating in an effort to slow the spread of the virus. There are two main types of coronavirus test kit, and in this article we will be giving you the low-down on what they are and how they work. But first, let’s clear up some jargon.  

What’s the difference between coronavirus, COVID-19, and SARS-CoV-2? 

SARS-CoV-2 (commonly known as coronavirus) is the name of the virus that causes the disease COVID-19. Viruses, and the diseases they cause, often have different names. For example, HIV is the virus that causes the disease AIDS.

The media often refers to SARS CoV-2 as “the coronavirus”, but there are, in fact, many different types of coronavirus.

SARS CoV-2 is the “new” type of coronavirus that was announced on 11 February 2020. This is the type of coronavirus that is currently infecting hundreds of thousands of people around the world. 

To summarise this in one sentence: SARS CoV-2 is the new type of coronavirus that causes the disease COVID-19

The two main types of coronavirus test

The two main types of test that can be used to detect SARS-CoV-2 are:

  1.  antigen tests (which indicate if a person currently has COVID-19); and 
  2.  antibody tests (which indicate if a person has previously had COVID-19 [and if they may now have immunity to SARS CoV-2]).

Testing for current infection

Antigen tests use a swab to take a sample of cells from the nose or throat of a person thought to be infected with coronavirus. The swab is then processed in a lab which looks for the virus’ genetic material to find out if it is currently present in the person who has been swabbed. 

Testing for past infection

Antibody tests involve taking a small sample of blood to test for specific antibodies called IgM and IgG antibodies. When a person gets infected by a virus, their immune system produces IgM and IgG antibodies to help fight it. These antibodies also remember how to deal with the virus in the future, so that the body can fight it off if it appears again.

Antibody tests are able to detect IgM and IgG antibodies and, as a result, indicate if a person has been infected by coronavirus in the past. Current antibody tests involve sending a small sample of blood to a lab, but it is hoped that in the near future there will be a reliable home-based test which can give an “on-the-spot” reading within 10-15 minutes. 

Which kind of coronavirus test do I need?

I want to know if I currently have coronavirus

Antigen tests are able to tell you if you are currently infected with coronavirus. It is best to use this kind of test when you have symptoms of COVID-19 (which include a new persistent cough and/or fever). 

Some scientists have suggested that it’s possible to be infected by coronavirus without showing any symptoms. This is known as asymptomatic infection. Therefore, if you’ve been in contact with someone with COVID-19, you may want to take an antigen test even if you have no symptoms.

You should also be aware that it can take up to 14 days to develop COVID-19 symptoms. This means that even if you’re asymptomatic (showing no symptoms) and get a negative result with an antigen test, you could still be in the very early stages of infection. Therefore, it’s best to repeat the antigen test if you develop symptoms of COVID-19. 

If you take an antigen test, it’s important to make sure that the person taking the swab is suitably trained and wears personal protective equipment (PPE). This is because collecting a sample from the throat or nose could expose the person doing the swabbing to infection. 

I want to know if I have previously had coronavirus

Antibody tests are able to tell you if you have been previously infected with coronavirus and if you now have immunity to it. 

You should be aware that it takes time for the body to develop IgM and IgG antibodies after infection, so it is best to take an antibody test at least two to three weeks after developing symptoms. It is thought that once you’ve had the virus and develop antibodies for it, you are very unlikely to catch it again. However, because coronavirus is such a new virus, scientists are not currently sure how long immunity lasts. 

How accurate are coronavirus test kits? 

As SARS-CoV-2 is a “new” type of coronavirus, work is still being undertaken to understand and improve the accuracy of the latest coronavirus test kits. With this in mind, it should also be understood that no test is 100% accurate. 

The accuracy of antigen tests — tests which use swabs to collect a sample — rely on good swabbing technique. Further, the antigen test is only reliable if it’s taken during the time the virus is present in the body, so a negative result does not rule out past infection. 

Antibody tests — tests that detect the presence of antibodies in a blood sample — are thought to be reliable. However, an antibody test result could still deliver a negative result if the person taking it has been very recently infected. This is because it takes time for the body to develop detectable IgM and IgG antibodies. 

In the future, it is likely that “on-the-spot” blood tests for antibodies will become available for home use. For now, though, current antibody tests require the person taking the test to send their blood sample to a lab to get a result. While this may not be as quick, these antibody tests are likely to prove useful in the fight against coronavirus. 

The bottom line

Testing is crucial to help monitor and prevent the spread of COVID-19. Antigen tests using nasal and/or throat swabs can detect current infection, and antibody tests using blood samples can detect past infection. 

Increased testing may also make it easier to treat people with COVID-19 in the future, as testing health and social care staff could identify which workers are safe to work so that they can continue to provide care for those in need.

Until more information is known about immunity to SARS-CoV-2, you should keep following government and Public Health England guidance on social distancing, self-isolation and shielding.