2 days, 3 tests, 3 results: Patients alert for Drastic Discrepancies in Antibody TestingHealth | December 2, 2021, Thursday // 16:45| views
Can you get a green certificate for antibodies? Maybe it depends on how persistent you are and how many times you try.
Patients are alarmed about drastic differences in the result of samples taken in different laboratories. Sometimes the samples are taken in a day or two, other times - only a few hours apart. It turns out that the result of one laboratory may be sufficient for a green certificate, and in another - noт. Or one result exceeds the other.
An OFFNews reader said she contracted COVID-19 in the spring and asked to have her antibodies measured to get a green certificate. It turned out to be insufficient - 120 units (BAU/ml) out of the required 150 for a certificate. Her friend and medical student told her that she had been tested several times for antibodies so she could attend lectures. He obtained three different results from three laboratories, the last of which was over the required 150 BAU/ml. When she realized this, our reader tried her luck in another laboratory. And so it turned out that her antibodies had increased from 120 to 250 units.
Consumer forums and lab pages on social media are full of such signals.
"Two days ago I did an antibody test in lab XX and the result was 21. Today I did in lab YY and I have 151. How do these things happen?" Wrote a user.
"62 in one lab and 466 in the other," added another.
The inaccuracy of antibody tests was the main argument for not recognizing them as a European green certificate. Many experts in our country expressed doubts about the extent to which they are indicative of protection, but subsequently the Ministry of Health decided to issue a local certificate to people with antibodies above 150 BAU/ml. This certificate cannot be used for travel abroad.
According to Dr. Todor Zahariev, one of the owners of Bodimed Laboratories, these differences may be due to the different methods used. Most antibody tests measure IgG (Immunoglobulin G), which is generally an indicator of past infection. However, in SARS-CoV-2 they also positive in active infection - something that is extremely atypical, explained to OFFNews Dr. Zahariev. According to him, this is one of the possible explanations for people with rising antibodies in the next test - a reunion with the virus.
Another reason for the differences between the different laboratories, according to the specialist, may be the control of the measuring devices. "At the beginning of the day, the device is started and calibrated. This is sometimes more expensive than the reagent itself. Unfortunately, sometimes this is not done, and this can lead to inaccuracies," he added.
Deviations can also come from the recalculation from one unit of measurement to another, because after the ordinance of the Ministry of Health all tests are recalculated in BAU/ml.
Last but not least is how the sample is stored and processed. However, this hardly gives large deviations, as these samples are stable at a temperature of 2-8 degrees for up to a week, the specialist explained.
He himself thinks that measuring antibodies doesn't make much sense. "This limit of 150 BAU / ml is nowhere in the world. No one can explain where immunity begins," said Todor Zahariev. According to him, it is not correct to compare results from different laboratories, and if a person wants to compare his own result, his recommendation is to do it in the same laboratory.
The same direction was given to OFFNews by another large chain of laboratories - "Cibalab", when we asked them to comment on the topic.
The EU and the US do not recognize antibody tests as a guarantee of immunity, respectively. do not issue certificates on this basis. Here is what the EC points out as an explanation:
"The detection and quantification of antibodies cannot be used as a direct indicator of protective immunity and there is no comparative analysis and comparison between different antibody tests across the EU.
Although a positive antibody test may be evidence of a past infection, it cannot give any indication of the time of infection. Therefore, it is impossible to determine the period of validity of the certificate. Even if antibody tests provide some evidence of an immune response, it is not known whether antibodies provide sufficient protection or how long that protection will last. They may become undetectable soon after a positive antibody test. It is also not yet known whether antibodies detected by currently used commercial tests would prevent infection with new variants of SARS-CoV-2. There are a huge number of antibody tests and comparing the results is extremely difficult."
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