Immunoglobulin D and gamma-interferon levels provide a relatively accurate picture of immune protection, but should be evaluated by a specialist.
Drink two glasses of water before the test to prevent discomfort when taking blood
After being vaccinated or having COVID-19, many want to know if they are already vulnerable to the virus. The body builds an immune defense, but how big is it and can it really protect us from re-infection? In search of the answer, people often resort to tests to test for available antibodies. But to what extent can they be trusted?
How many types of tests for antibodies and how do they differ?
Two types of tests for so-called humoral immunity are most commonly offered, namely immunoglobulin D testing, which is the main mechanism by which so-called antibodies are made. The first is qualitative, the second quantitative. This does not mean that the latter is worse, but that it evaluates the amount of antibodies that have formed. And the quality only shows whether there are any antibodies with a titratable number below and above 50 units. It only shows whether they are available at all, while the other examines their quantity and effectiveness.
A qualitative test can only determine whether or not the organism has encountered the virus and can also be performed with peripheral blood at home.
And the number of antibodies with neutralizing capacity is tested quantitatively. It is made in a laboratory. A lot of venous blood is taken and parts of the coronavirus are inserted into the patient’s blood serum to determine how “well” they are repelled. Although both tests do not guarantee 100% certainty, it can be said that a positive test for antibodies with neutralizing capacity almost always means that a person is protected, explains Thomas Lorenz from the Union of German Laboratory Physicians. According to him, the first type of tests is not very useful. The virus neutralizing capacity is considered to be at least 1200 units of the immunoglobulin G in question.
Immunologist Prof. Carsten Vacl notes that tests for antibodies with neutralizing capacity are more accurate, but ordinary tests also provide an answer to the degree of protection. The reason is that there is a relationship between the level of antibodies and the level of antibodies with neutralizing capacity.
At this stage in our knowledge of the coronavirus, however, it is difficult to say what level of antibodies are needed to make sure a person is fully protected.
What types of antibodies are there?
Of interest are mainly three types of antibodies. The first two – the so-called. immunoglobulin A and immunoglobulin M, occur as a result of the body’s initial reaction against the virus. They are formed quickly, but their level in the blood decreases in a relatively short time after infection compared to those of the third group – the so-called. IgG antibodies. They are formed by “memory cells”, some of which can remain in the body for a long time. They “remember” that the Sars-CoV-2 virus is an enemy. “Anyone who has ‘memory cells’ can quickly produce many new antibodies if needed,” explains Professor Vacl.
When a test makes sense for antibodies?
The body begins to produce IgG antibodies only a few days after infection. Therefore, the test that checks for this type of antibody should not be done until at least two weeks have passed since the infection. However, if the test checks for IgM antibodies, it is possible that it will be negative a few weeks after the infection.
What if the antibody test is negative?
This does not necessarily mean that protection against the virus does not exist. “There are people in whom the infection has passed slightly and the concentration of antibodies is falling rapidly,” explains virology professor Marcus Paning of the University Hospital in Freiburg. However, they may also be protected from recurrence.
The reason is that in addition to different types of antibodies, the body has another way of protection – the so-called. T cells. Unlike antibodies, they do not attack the virus to prevent infection, but they do destroy the cells infected with the virus and thus play an important role in the immune response. Tests for the presence of such cells are also offered by laboratories. For example, the study of gamma-interferon – another specific protein that shows the presence of lymphocytes. Some laboratories offer other types of cellular immunity tests that are considered more accurate. But anyway, the study of cellular immunity is a very specific job and the results must be interpreted by an immunologist. A variant of the activated lymphocyte test, which is considered more accurate, is the so-called ELISpot, which detects even one in 200,000 activated cells that secrete specific gamma-interferon against SARS-COV-2.
There is no guarantee
Antibody tests on the market do not provide sufficiently reliable information to protect against future infection. They are only able to detect past infections or an immune response after vaccination. However, how long this immune response will protect the body and to what extent is still unclear.
According to US health authorities, antibody tests are only useful for epidemiological studies, not for diagnosis, protection or resumption of socialization. However, these may be lobbyist claims by advocates of so-called PCR tests. The whole AIDS epidemic is being controlled without any PCR tests, not even analytical (quantitative) measurements for HIV. Everything is just a quality test for antibodies, so this method of testing should not be underestimated in any case.
Are the results of
test for antibodies against COVID-19?
The antibody test is a simple blood test and does not involve major health risks. The risk is that an incompetent tester will not be able to hit the test vein and rupture it. In this case, heparin ointment is recommended at the injection site. It is recommended to drink at least two glasses of water before the test – this way the veins swell and the blood becomes more fluid, thus avoiding slight pain or discomfort. However, it is important to keep in mind that antibody testing can have misleading results. The test result may be false positive, ie. have no antibodies to SARS-CoV-2 and have not been exposed to the virus in the past. The test can also be false negative, ie. however, you may be infected with SARS-CoV-2. You may not have a detectable level of antibodies or you may have been tested too soon after infection. Regardless of the result of your antibody test, you can still become infected or spread the virus to others.
Can antibody testing predict immunity?
The antibody test alone is not convincing enough to predict sustained immunity. It remains unclear how long the antibodies remain in your body after infection with COVID-19 and how many antibodies are needed to neutralize the SARS-CoV-2 virus after re-exposure.
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