The number of people with coronavirus infection is growing every day all over the world, therefore, those who want to know whether there is a COVID-19 pathogen in the body or not, what is the probability of the disease. For diagnostics, certain studies are carried out. At the same time, topical questions arise: what kind of analysis is needed, when and where can it be taken, how to interpret the result? Let's try to figure it out.
Do I need to take a coronavirus test?
Perhaps we should start with the cases in which you need to go to take a test for coronavirus.
Such a need arises when there are signs of the disease, with possible contact with patients and carriers of SARS-CoV-2. But given that the symptoms of the sick can be varied, and the communication of people does not allow accurate tracking of contacts, there are always a lot of people who want to be tested for coronavirus. Firstly, not everyone can afford to take this analysis because of its high cost. Secondly, as in the case of testing antibodies in the body, which usually appear after an illness, the result may not be informative at all. Or vice versa, waiting for your turn for analysis, the result may not be relevant at all. Therefore, the delivery of biomaterial will be absolutely useless, but at the same time, the risk of disease increases while staying in public places on the way to the institution where the tests are taken. In some cases, such a risk will be completely unjustified.
So, blood donation for coronavirus infection is recommended for the following groups of people:
- Those who have been abroad and have symptoms of SARS.
- In case of confirmed or suspected pneumonia.
- People over 60 with symptoms of SARS.
- People with chronic diseases and signs of SARS.
- People who returned from another country within the last 2 weeks without visible signs of SARS.
- People with symptoms of SARS.
The number of the group of people corresponds to the number of the importance of passing the test for the presence of coronavirus infection in the first place. However, although the final decision remains with the attending physician, everyone can take such a test on their own. Moreover, in all countries, the conditions for delivery may differ, because each country has the right to choose its own ways to combat coronavirus infection. One thing is clear that such a study definitely takes place on a commercial basis, and the results usually need to wait up to 4 days. At the same time, biomaterial sampling can be carried out at the patient's home by a specialized mobile team, or directly at the point of analysis.
What tests for detection of the causative agent of COVID-19 are available today?
To date, there are several types of detection of the pathogen COVID-19 (SARS-CoV-2). All of them have their own characteristics and differences. Moreover, these differences relate not only to their purpose, but also to the method of taking the biomaterial.
- PCR (polymerase chain reaction) is a test for the diagnosis of SARS-CoV-2, which involves taking a swab with physiological discharge from the patient's nasopharynx or oropharynx. It is desirable to carry out the procedure in a specially designated and isolated room, although at present the material is taken at home. For reliable results, the patient should not take absorbable or sprayed medicines into the oral cavity 6 hours before the procedure. And also you need to exclude drinking, eating, smoking, brushing your teeth and chewing gum 3 hours before the procedure. The pause between drinking alcohol should be as long as possible due to the ethyl alcohol in its composition, which has an antiseptic effect. The SARS-CoV-2 coronavirus lives inside epithelial cells. For PCR testing, it is important to obtain a swab with a sufficient number of infected cells. To recognize a coronavirus infection by the polymerase chain reaction method, it is required to extract a site potentially containing a single-stranded RNA virus from the patient's physiological fluid. Then, the double-stranded DNA modeled on its basis is repeatedly cloned using the polymerase enzyme, a process called amplification. In case of successful amplification of this area, the result for the presence of the virus in the body will be positive. The turnaround time for the result varies, but in general it takes no more than 4 days.
- Detection of specific antibodies against SARS-CoV-2 in a patient's blood is a good choice for rapid, simple and highly sensitive diagnosis of COVID-19. ELISA (enzyme-linked immunosorbent assay) analysis requires taking the patient's venous blood. As a rule, an appointment for this manipulation is not necessary, as well as special preparatory measures, in particular, you can smoke and take an analysis at any time of the day. However, it is worth observing a 3-hour pause after eating. A person who takes tests to determine the presence of antibodies to coronavirus should not have clinical manifestations of an infectious disease in the acute phase: fever, cough, runny nose, muscle pain. Unlike the PCR test, which establishes the true presence or absence of a virus in the body, the ELISA test only shows the result of the body's reaction to contact with the virus. IgM are the first antibodies produced in an immune response. Detection of IgM antibodies may indicate recent infection with SARS-CoV-2. IgG antibodies are responsible for immunological memory and long-term immunity. That is, the presence of IgG antibodies in the blood may mean that the patient has already had the disease in an asymptomatic form. In the absence of these, the body did not encounter the virus. There may also be a borderline result, which implies a small amount of IgM and IgG antibodies. This means that either the disease is asymptomatic, or the virus is present, but only at the initial stage of development, in which case it is recommended to retake the test in 10-14 days. The level of antibodies and the dynamics of the immune response in different people may differ. It depends on the state of the human immune system, the presence of concomitant diseases and other factors. In particular, with COVID-19 , immunoglobulins begin to form on average 7-14 days after exposure to the virus. It is important to understand that since antibodies do not begin to be produced from the first day of infection, the test for immunoglobulins can also be negative, because testing can fall on a period when the body has not yet had time to form an immune response.
- EMG is a test jointly developed by Russian and Japanese scientists. Actually, the name of the test is the abbreviated name of the company "Evotech-Mirai Genomics". Although this is a completely different method for detecting a virus in the body, it is based on the PCR method - DNA amplification. But in this case, SmartAmp isothermal molecular diagnostics is used, which skips the long stages of heating the material as in PCR, which reduces the time to obtain a reliable result. This whole process takes only 30 minutes. However, the material for analysis is taken in the same way as for the PCR test - from the mouth or nose. Therefore, for its implementation, you should also prepare in advance.
- Other express systems are being developed in the world. At the moment U. S. The Food and Drug Administration approved the type of tests. The method for detecting a virus is quite simple: in the presence of a virus in a biomaterial, CRISPR enzymes produce a glow of viral cells. Therefore, the result of such an analysis can be obtained within an hour. The biomaterial for the study is also taken from the nose, mouth, throat, or liquid from the lungs can be used. Therefore, to obtain a reliable result, preparation is also required, as for a PCR test.
- Appeared in the world and the development of recognition of coronavirus using artificial intelligence. This does not require biomaterial, because it is an electronic sensor in the form of a patch, which is glued in the area of the jugular fossa, and reads the respiratory rate, sounds, and various activities. As soon as it detects a coronavirus, or rather changes in breathing, it will notify the user. However, this type of diagnosis is not suitable for detecting an asymptomatic coronavirus infection, but only a severe form in the initial stages, more precisely the development of pneumonia.
Depending on the chosen test for the detection of coronavirus, the analysis can be carried out in various places. The very first and most common place where such a study can be carried out is in the clinic, having previously received a referral from the attending physician. In cases where the patient cannot break self-isolation, a special team can be sent to the patient's home. Most often, the PCR method is used.
At the same time, as mentioned earlier, it is possible to conduct tests without a doctor's referral in commercial organizations: laboratories and medical institutions. In this case, research options will be wider, but it all depends on the available equipment.
Passing rapid tests is very popular. No wonder their use is recommended at airports and train stations.
- Nature.com. – First CRISPR test for the coronavirus approved in the United States.
- Phc.org.ua. – What to know about enzyme immunoassay (ELISA) tests for COVID-19.
- Сoronavirus-control.ru. – Where and how to get tested for coronavirus.
- Rospotrebnadzor.ru. – About recommendations on how to prepare for the PCR test for COVID-19.