Tuesday , May 24 2022

Index – Economy – PCR, rapid test, antibody – why are there so many Covid tests?


We read more test data almost daily, in some cases what kind of test they did, and at other times we only see the numbers themselves.

Why do you need such a test?

In short, each has a yearly raison, each one useful for a different reason test.PCR

Why is the PCR test the standard, the most accurate?

Using an enzymatic reaction, viral inheritance, a ribonucleic acid (RNA) sample of SARS-CoV-2, or Covid-19, is expanded to be available in detectable quantities. The test is ideal in principle, as it is unmatched in all the parameters that can be considered when evaluating tests of a similar nature, ie sensitivity and specificity (simply the ratio of negative to false positive tests).

If this is so clear, then why do we need another test?

Unfortunately, PCR is very time consuming, specialized, and time consuming, and also costs a considerable amount of equipment and chemicals to perform. There is also the possibility of errors here, such as inadequate sampling, lack of patient cooperation, but most of all problems can arise during storage and transportation of the sample: RNA is highly sensitive to all external influences and even age storage temperatures, so it could degrade. , before it enters the PCR machine, which can lead to a false negative result, even if it was not caused by the PCR error itself. The main disadvantages of the test are therefore very time consuming, cost and very limited availability. To counteract these, what’s called rapid tests.

They also detect the components of the virus, but in a different way, usually based on the phenomenon of fluorescence. They are much faster, can be made locally, and do not require any special expertise to perform, but only training. These tests, unlike PCR, can only reliably detect some virus, but this is not necessarily a disadvantage. Practically every day, we are primarily interested in the clinically significant amount of virus, ie whether the person is currently infected or infectious. For example, the Rapigen Biocredit test, manufactured in South Korea and used in Hungary, detects the presence of viral RNA with a sensitivity of over 90% and specificity of almost 100 percent. based on. Of course, this is only true if the sampling is done correctly and the patient has followed the requirements for a successful test, ie they have not eaten or brushed their teeth before the test, etc. This is because the rapid test, like PCR, is based on nasal sampling.

Rapid antigen test in Germany

Rapid antigen test in Germany

Photo: Matthias Schrader / MTI

This brings us to the third type of test, which is no less

These are done by taking blood and, unlike previous tests, do not detect the components of the virus, but the antibody formed against them. Antibody production takes time, so these tests are more likely to determine whether we may already have acquired the infection or whether we have developed protection against the virus. This will be essential after the advent of vaccines, but such screenings are still important, especially given the spread of plasma treatment, and also of public and epidemiological importance.

(Cover image: A sample of a man’s oral cavity is taken at a clinic designated for coronavirus screening at Mohács Hospital on May 12, 2020. Photo: Tamás Sóki / MTI)

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