It is still difficult to determine whether someone has had the corona virus in the past. The antibody test, the most suitable test for this, has important limitations. In some cases, such a test can help a doctor to find the cause of long-term complaints.
General practitioners are regularly asked by patients whether they can undergo a test to demonstrate whether they have had the coronavirus in the past. This is what Stijn van den Broek, spokesperson for the Dutch College of General Practitioners (NHG) and general practitioner, says. The NHG generally advises against doing this type of test. For people with long-term complaints that may be caused by the corona virus, GPs sometimes request an antibody test.
Antibodies are part of your immune system. Some antibodies help prevent a virus from making you sick. Generally, antibodies are only active against one specific virus.
If you become ill due to the coronavirus, your body may subsequently produce antibodies against this corona virus. With an antibody test you try to determine whether these antibodies against the corona virus are present in the blood.
Why are antibody tests generally not recommended?
Van den Broek explains that the antibody tests are generally not recommended because they provide little useful information. “If the test result is positive and antibodies against the coronavirus have been found, then you have most likely had COVID-19. But we do not yet know whether you are also immune to the coronavirus. get sick, or spread the virus to others. ”
In addition, with a negative result, according to Van den Broek, it is possible that you have already had the corona virus. For example, it seems that people with mild symptoms sometimes do not produce antibodies at all after a COVID-19 infection. Antibodies can also disappear over time.
Sometimes testing for people with long-term complaints
Van den Broek explains that a GP nevertheless sometimes has an antibody test done. “If someone comes by with long-term complaints, then as a general practitioner you and the patient will try to find out where these complaints may come from. Blood tests, including for antibodies for the corona virus, can be part of this.”
“At the moment, COVID-19, just like mononucleosis or flu, may be the cause of some long-term complaints. That’s why you want to be able to test for this, especially if someone has had symptoms that match COVID-19 and they have not been tested. is when the symptoms were there. “
No antibodies test 100 percent reliably
Van den Broek explains that the analysis of these antibody tests always takes place in a reliable laboratory, where a specialist can help interpret the results. RIVM states that the tests used for this are suitable for individual patients if they are done at least two weeks after the first complaints that fit COVID-19.
The RIVM states that no antibody test is 100 percent reliable. It is possible that someone wrongly receives the result that he has produced antibodies, or incorrectly receives the result that he has not produced antibodies. According to the RIVM, the chance that a positive result is correct is greater when someone is tested who had complaints that match the corona virus, than when a random person is tested.
Rapid tests unreliable
The RIVM and NHG do not recommend the use of rapid tests, which are sometimes offered online. Rapid tests are not analyzed in a lab. You do them at home with the help of a drop of blood, after which you see a positive or negative result after some time, just like with a pregnancy test. These tests proved to be too unreliable so far.
When is an antibody test reliable enough?
- The Serology Taskforce consists of scientists from RIVM, universities and laboratories. According to the Serology Taskforce, an antibody test for the coronavirus is sufficiently reliable if they are done a minimum of fourteen days after the first symptoms of COVID-19 are done and the test meets the following two criteria:
- When a hundred people are tested, a maximum of two people may receive a result that incorrectly indicates that they have produced antibodies against the corona virus.
- When a hundred people are tested, a maximum of five people may receive a result that incorrectly indicates that they have not produced antibodies against the corona virus.