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What is an antigen test?

Diagnostic tests are used to identify SARS-CoV-2 virus infections. Rapid antigen test or rapid test (English. Rapid antigen test) that does not need to be sent to a laboratory but the test result can be obtained directly on site. Antigen testing is primarily an important tool for detecting and preventing the spread of covid-19 and is an important tool for determining whether an individual should be isolated.

What is an antigen? And how does an antigen test work?

Description of what an Antigen is.

The body has an ingenious defense that identifies all the proteins in the body that do not match your own genes. The body further thinks that this protein should be captured and destroyed.

When the body has identified such a foreign protein, your white blood cells create a so-called antigen, the purpose of which is to capture and destroy these foreign proteins. 

The first time the antibodies hit a new protein, it does not know how to fight it, but the antibody gradually learns how to fight the foreign protein. It becomes, so to speak, better at capturing the previously unknown protein.

It is then said that an anti-gene is created because the protein creates new potent antibodies.

An antigen test briefly tries to identify these antigens. To find the antigen, you must then have an antibody because the antibody, as I said, can identify and destroy the antigen

SARS — COV-2 tests typically use antibodies created in animals to hunt and identify the proteins that are embedded in the coronavirus surface. If the animal's antibody succeeds in detecting viral proteins, the person is very likely to have an ongoing corona infection.

When you are going to take an antigen test, it starts with medical staff using a stick to catch mucus from your throat or nose. Then the person taking the test takes you and dips the stick in a liquid to loosen the virus. Then you take the liquid on a test cassette that is coated with antibodies. The good little antibodies can then capture coronavirus proteins and a line becomes visible on the test plate.

 Disadvantages of antigen tests include, but are not limited to:

 the tests are not 100% reliable. If there are not enough malicious virus proteins, it is not certain that the antibodies will find the protein. If you have been ill for a long time with a low proportion of proteins, it can also be difficult to find.

When using antigen tests, one should therefore at the same time consider whether the person has any other symptoms or the like. But since the antibodies only react if they find the protein, a positive test with very high security is correct.

 Advantages of antigen testing:

 The biggest advantage of the antigen test is that it is fast. That is, the antibody on the test plate reacts very quickly to the protein and the response comes within a maximum of 15 min.

What is the sensitivity of an antigen test?

The sensitivity indicates how many of the tests have false negative answers. The sensitivity must be 90% to be approved by the EU Health Security Committee. As explained above, there is a risk that you do not have enough protein in your mucus for the antibodies to be able to capture them. However, most antigen tests have a higher sensitivity.

The specificity of an antigen test

 The specificity, on the other hand, shows the risk of a false positive answer. As described above, it is only a positive result if the antigen succeeds in capturing a protein. The specificity of an antigen test is therefore very high and EU Health Security has stipulated a minimum specificity of at least 97%

Other guidelines for a test to be approved within the EU


  1. They have a CE mark
  2. Meets minimum sensitivity over 90% and 97% specificity
  3. Approved by at least one Member State, specifying details of results of studies in the country concerned


Feel free to contact us at Birga Care if you want more information about how an antigen or an antigen test works.

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