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FAQ
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WHAT IS THE ACCURACY OF THE TESTS? (SENSITIVITY AND SPECIFICITY). *
Test sensitivity - 93%, specificity - 100%. In a practical sense, this means that if you get a positive result, then with a probability of 100% the SARS-CoV-2 antigen has been detected. Moreover, if a negative result is obtained, then with a probability of 93% the patient does not have the SARS-CoV-2 antigen. This does not mean that the RNA / DNA of the virus cannot be detected in the patient, perhaps, if there are traces of the virus, at maximum Ct PCR cycles, this is possible, because the RNA / DNA of the virus is present longer in the body, even after the virus is no longer able to cultivate and the person is not contagious and depends on the type of sample. Nevertheless, it is a negative antigen test that indicates that either the virus is completely absent, or the antigen nucleocapsid protein containing the enzyme necessary for its reproduction has not been detected.
* Confirmed sensitivity and specificity during clinical trials in Russia.
ANTIGEN OR ANTIBODY, IGG / IGM?
When does it make sense to use antigen tests and when antibodies? In the acute period, that is, during the period of onset of symptoms and the onset of the disease from 1-7 day justified using a test to determine the antigen, that is, the virus itself, as long as it is present in the body. Due to the high sensitivity and specificity of the C-test AG Covid-19, the virus is detected even with a minimum viral load.
From the 5th day, antibodies are usually formed. Antibody tests are effective at this time. It is important to note that IgG and IgM antibodies appear at different times, and the intensity of staining in the presence of experience with such tests, suggests the duration of the course of the disease. In other words: antigen - "is there a virus now", antibodies - "was it Covid-19 and is there any antibodies".
PCR OR ANTIGEN?
It must be remembered that the two methods differ and the use of each specific one depends on the diagnostic purpose. As simply as possible: the PCR test will tell you whether a person is sick or not, or whether he was sick, in addition, you can roughly assume a viral load depending on the cycle. From the result, the test for Antigen, it is possible to understand not only whether a person is sick or not, but also whether he is able to transmit the virus to another person, and also suggest the level of viral load depending on the brightness of the "T" line color. In addition, it must be remembered that the PCR method is instrumental, while the express test is used without additional equipment (reader).
IS AN ANTIGEN POSITIVE TEST POSSIBLE WITHOUT SYMPTOMS?
This happens and is often due to the fact that a person is an asymptomatic carrier. The test has a high sensitivity, which makes it possible to detect the virus even at its weak concentration. The presence of symptoms refers to the individual characteristics of the body, and this does not mean that the virus is absent in the body.