MIC: How can patients understand the results of an antibody test? Which antibodies appear at certain stages of the disease?

Trickovic: Serological methods detect the presence of antibodies, ie. certain classes of immunoglobulins (IgM, IgA, and IgG) in the patient's blood, which are produced in the body in response to the presence of the virus.

The appearance of antibodies in different stages of SARS Cov 2 infection 

IgA is the earliest immunoglobulin that occurs after infection with the SARS Cov 2 virus, a few days after the onset of symptoms. IgA antibodies are early antibodies that are concentrated in the mucous membrane of the throat, nose, intestines and secretions in a fresh infection. After IgA antibodies, the body synthesizes IgM antibodies. It is a significant marker and is used by almost everyone. IgM antibodies reach their highest level in the blood a week after the appearance of the first symptoms of the disease, and then decrease, so that in the third week from the beginning of the disease, they generally cannot be found in the serum. IgG antibodies begin to form in the second week of the disease and reach their highest level about 4 weeks after the onset of symptoms. Approximately 6 weeks after infection, 94-98% of patients show elevated levels of IgG antibodies. These antibodies stay in the body for a long time and are an indicator of a previous infection.

MIC: IgA antibodies have not been mentioned in our country so far. You are among the first to research these antibodies overall, so tell us what their significance is.

Trickovic: We started working on IgA because it is the first antigen that is created, the first that is synthesized,literally after one to two days after the onset of symptoms. It lasts for a short time, 3-4 days. That was the reason why we started developing antibody tests.

Naissa cartridges with blood samples

However, in parallel, studies have shown that IgA is specific for respiratory infections, which means that if you detect IgA in a patient, he will have problems in the respiratory tract. This is just one of the typical things, clinically useful. When we looked at who in the world did all the research on IgA antibodies, we came across a study done at the University Hospital Center in Hamburg, where they proved that a very large number of patients who were detected with IgA class antibodies, passed easily the covid virus. This means that if you find out that someone has already developed antibodies on the first or second day, their body is fighting well. What our studies showed during the time we were doing the validation of the test, the samples of hospitalized patients, the ones on the respirators, we could not find anything - the complete absence of antibodies. This is proof that the body's immune response reacts later or is absent and these are for the most part very severe cases.

Table showing the appearance of antibodies by days

We can have a realistic diagnostic prediction, according to a German study, that someone will pass easily if their IgA is high at the very beginning, after encountering the virus. IgM also showed that if it reacts high quickly, and the infection is active, then you get two things: you get a patient that is certainly infectious, you also get information when he had contact with the virus and when he got IgM antibodies. In that case, you can monitor the course of the disease, and you can expect an increase in IgG antibodies in, say, 7 days after that.

MIC: How is the NAISA test you do different from other serological tests?

Trickovic: There are still no international standards and units for the antibody values in Covid patients. You do not have it because it is still a new virus and it does not have any standards. With other tests for establishing the level of antibodies, you have one point and to that point, all the values are low values, and above that point all the values of the antibodies are high, i.e. you do not have values of the antibodies expressed in some numbers.

Laboratory for testing for the presence of Sars Cov 2 virus

What did we do? Neomedica has made its standards, its reference and the result that our system issues, we publish in some of our units, NAISA units. But the advantage over other tests that exist, which are not quantitative, but qualitative, is a big difference because we always give the same number, the same level in units, the expressed number of antibodies that we detect. Then you can monitor from patient to patient the fixed difference in the level of antibodies. Our test is different from most others, especially from these current fast tests that are done because it is quantitative and the exact value is monitored.

MIC: Do you have data on the level of IgG in those who became infected at the beginning?

Trickovic: It is very individual. We have, for example, individuals whose antibodies have completely disappeared after only a month. We have individuals who have these antibodies after two and a half or three months, but the level is one coma something. We had the same case where the person was claiming to be recently infected. According to the results, we only see that IgG is low, and to our knowledge, it is an old infection. And then it turned out that two months ago, everyone in the office was sick except him, who had actually easily overcome the virus. His colleagues were hospitalized, and PCR positive, and we saw from the results that he had the same. That's the advantage of NAISE and what you can see - it would be great for doctors to interpret.

MIC: It has been proven in the world, and there have been cases of reinfection in our country as well. What do your experts know about this?

Trickovic: We caught reinfection one and a half month ago. We did not publish the news because a small number of reinfected samples were proven and were not representative of the study. But we measured. We found IgM in those samples, these are the same donors who did not feel the symptoms, but knew that they were infected.

Sasa Trickovic, the founder and general director of the company NeoMedica

They donated blood again, and we saw an increase in IgM, their IgG was already falling by then. When IgM jumps, IgG starts to rise again. And here you see exactly that it is a reinfection. But what is good? The symptoms were mild, or there were no symptoms at all. They could pass easily and not know about their situation. We advised them to call the doctor again, let them do a swab test, because they are contagious, they are carriers. Caution is needed here.

Sasa Trickovic is the founder and general director of the company NeoMedica doo Niš, which has existed since 2000 and is engaged in the production and sale of diagnostic medical devices. The family business has grown into a company that exports its high-tech products worldwide. One of the more well-known examples is the supply of the Egyptian health system with hematological reagents and devices for the last four years, which has placed NeoMedica among the leading Serbian export companies in the Egyptian market. In addition to hematology, NeoMedica innovates and produces In-Vitro medical devices in the field of immunochemistry, especially in the detection of viruses, infectious diseases, hormones and tumor markers.

Author: Jelena Djukić Pejić

Translation: Mladen Djordjevic