SARS-CoV-2 (Coronavirus) PCR method test

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ADDITIONAL INFORMATION REGARDING THE DETERMINATION OF A COVID-19 INFECTION

Currently, two types of tests are performed: the PCR (molecular) test for COVID-19, which is performed from the nasopharynx and is suitable for early diagnosis of the disease, and the serological test for the detection of antibodies to COVID-19 (IgM and IgG), which identifies the body's reaction to the virus.

The PCR test is performed by taking secretions from the nasopharynx and during the test it is determined whether the test material contains genetic information of SARS-CoV-2. When testing with this method, the highest probability of detecting traces of the virus is 2-7 days after infection. In the later stages of the disease, more time has passed after infection, the virus travels to the lower respiratory tract, so the test may not be informative, or it is necessary to take a test from the lower respiratory tract specifically. means to collect sputum. Therefore, a negative PCR test result cannot yet completely rule out infection.

Serological diagnosis - determination of antibodies to COVID-19 is performed by taking a blood test. As a result of this test, virus-specific immunoglobulins M and G (IgM and IgG) can be detected. IgM is the first antibody produced by the body in response to infections, IgG is produced later, its concentration is higher and it persists for a long time. This test is suitable for assessing whether there was contact with the virus, whether an immune response was formed, the prevalence of infection among a group of people, for the rapid identification of symptomatic and asymptomatic carriers. A positive result of this test does not allow us to say that the person is infected, as positive reactions are rare but possible in other (especially autoimmune) diseases, so it is recommended to confirm the diagnosis with a PCR test. The advantage of this test is that it is done faster.

NOTES: *In the case of a COVID-19 infection, the patient's condition may be in the "window period" during the test, which is the period from the beginning of the infection to the detection of virus antibodies in the blood, usually 10-14-21 days. This time is the early stage of infection, when the virus spreads rapidly. During that period, a PCR test should be performed, which shows the presence of an early stage of infection in the body.

It is important to know that after receiving a negative result of the PCR test, one cannot exclude the infection of COVID - 19, because the effectiveness of the PCR and antibody test is not the same at different stages of the progression of this disease. Several used diagnostic methods (PCR and IgM/IgG antibody detection) complement each other, improve the efficiency of diagnosis and allow efficient monitoring of disease progression.