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Feb 16, 2021
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PCR test – the gold standard of diagnostics

PCR test – the gold standard of diagnostics

The second wave of coronavirus infection in Russia is weakening, but it is still far from complete decline.

And although the word “covid” has been in the first place for a whole year, people, feeling unwell, still do not know what they should do first. And in fact, where should an anxious person turn, what should be his actions? These and other questions of the first deputy editor-in-chief of “MN” Andrey AVDONIN are answered by the doctor of medical sciences Gennady SHARAPOV, Head of the Center for Laboratory Clinical Diagnostics, FGBU “3rd Central Military Clinical Hospital named after A.A. Vishnevsky “of the Ministry of Defense of the Russian Federation.

– Of course, immediately be examined for COVID-19, that is, to pass a nasal swab for polymerase chain reaction – PCR (namely a PCR test, not an express analysis!). The earlier the diagnosis is made and treatment is started, the more chances of avoiding serious consequences.

INCREDIBLE DECLINE IN INCIDENCE

– Your center is equipped with the most modern equipment and, as I understand it, from the first days of the pandemic, it has been operating at maximum load. How do you assess the situation today?

– The peak of the second wave, which rose in August and continues to this day, fell in October – December, when the maximum incidence rate was detected both in Moscow and in Russia as a whole. Every day we collected material from 200 or more people, receiving 40-45 positive PCR results. And now we take material from 35-40 people a day, of which 1-3 are covid-positive. We are seeing not just a sharp, but a colossal decline in the incidence!

– Often, especially outside Moscow, you can wait 3-4 days for a PCR result. Is it possible to detect covid faster?

– The first diagnostic laboratory test that can be used is a complete blood count. By the number of lymphocytes and leukocytes, it is easy to suspect that the patient may have covid, even if he has not yet passed PCR. Well, PCR is the most common test for detecting coronavirus.

The second number is the study of hemostasis, that is, the biological system of the body, the function of which is to preserve the liquid state of the blood, and the determination of the level of D-dimer, a protein fraction, which is considered an indicator of thrombus formation.

We noticed that with moderate to severe coronavirus infection, the hemostatic system reacts first. Such patients need blood thinners. If doctors miss this moment, the possibility of death increases dramatically.

– If, according to a general blood test, one can suspect that a person is sick with covid, does this mean that people with a cold should start the examination with this particular test?

“It will just be a determination of the likelihood of a covid, what it might be. We get a blood picture typical of viral infections in general. And what kind of virus caused this picture, the PCR test, recognized as the gold standard of diagnosis, will show. So, if you suspect COVID-19, we recommend starting with it. Computed tomography of the chest organs and everything else is very good, but the most reliable way to find out if you are sick or not, I repeat again, is PCR diagnostics.

“IN OUR PCR DIAGNOSTICS WE ARE 100% SURE”

– Which test is better and what is their accuracy? At the airport in Paris, there was a case where 49 tests gave a false positive result.

– I don’t know about that, now we are working only with domestic reagents produced in Novosibirsk. They have proven themselves on the positive side. Disruptions are possible when a laboratory takes on too much research, which happened at the peak of a pandemic. Then operator errors occur. And not just mistakes, but contamination, that is, contamination of biological material directly in the laboratory. We also faced such things, when in April a wave of patients went and had to stand in 2-3 shifts. Then we said: no! We need a quality analysis. Let’s do a little fewer tests, but the results will be more accurate. Now we are 100% sure of the results of our PCR diagnostics.

– So we can assure readers that the Russian PCR test gives a 100% correct result?

– Yes, these are very good diagnostic kits, of high quality.

– Now such an analysis is done on average up to two days?

– Yes – up to two or three days, which is very bad. After all, all this time the infectious patient continues to communicate with family, colleagues, friends.

– Why do they take so long? Not enough equipment?

– Of course. We also “changed shoes” on the go, bought equipment, studied the mechanism of its operation in the shortest possible time and received certificates of specialists. We worked day and night to start conducting tests in April. If we hadn’t done this, the hospital would have been a disaster.

– Do I need to donate blood for antibodies to coronavirus before vaccination? There is an opinion: if they are, it means that the person has already had COVID-19 and there is no need for vaccination.

– Let’s talk about everything in order. So, we did PCR, the result was positive. If the patient has no complaints, it means that we are talking about asymptomatic virus carriers or mild COVID-19. Does the patient have a sore throat, no sense of smell, or a fever? It is necessary to determine the stage of lung damage – from the first to the fourth. We have tests that allow you to do this within 10 minutes.

– Without CT?

– Without CT!

– By biochemical blood test?

– By the level of C-reactive protein, ferritin and interleukin-6. The analysis, which takes 3-4 hours, allows you to answer the question of whether a person is threatened by the notorious cytokine storm or not. Recall that this concept means an extremely negative reaction of the immune system, which is also called the suicide of the body, as a result of which inflammatory molecules – cycotines – appear in the blood.

If there is no threat of a storm, expensive drugs are not used; if there is, one cannot do without them. It is important to introduce them to the patient in advance: when the storm has come and continues, the drugs mentioned above are already practically ineffective. We need a different treatment tactics.

– But if the stage of the disease can be monitored by blood analysis, what is it that we lack to do such express diagnostics for everyone? Equipment, qualified specialists? Money?

– Money. Yes, of course, it’s all very expensive! Not every clinic can afford it. In the first wave, when we opened the “red” zone in our hospital, we spent 40-45% of the annual budget in a month and a half. After that, they lived the whole year very difficult, because no one gives additional money.

– Is it true that if you buy powerful equipment, the cost of analyzes will drop almost 10 times?

– The way it is. But these tests cannot be put on stream in tens of thousands. They are specific, and when the pandemic goes away, they will no longer be needed in such quantities.

LONG-TERM IMMUNITY – IN THREE OF THE INVOLVED

– But what about antibodies?

– Now many have been ill with varying degrees of severity. The question arose: did they get immunity? Antibodies are of different types: immunoglobulins M and G are the most important in determining the stages of covid. First, M are produced, then their level begins to decline, it takes a month and a half, or even two. And you should be guided by the level of immunoglobulins G. Returning to your question: if this level is below 20-30 units, you can get vaccinated, despite the fact that you have had covid.

– With a low level of immunoglobulins G, can you get sick again?

– Can. True, since April I have seen no more than 10 repeated cases. Here, you see, this is the thing. You got sick and got a high level of immunoglobulin G – 120-300 or even 500 – the highest that I have ever seen. This is all great, but the question is how long this immunity will work. In many April patients who recovered from the first wave, the level of immunoglobulin G now tends to zero. So they need to be vaccinated.

I thought the more severe the disease, the more immunoglobulins G you get for a longer period. But it didn’t work out that way. I observe patients who have suffered mild COVID-19 and have received long-term immunity. And I see those who were seriously ill, but their immunity was short. There were 300 units of immunoglobulin G, and now there are 30. People are frightened, they think they will get sick again! I got the impression that long-term stable immunity is developed in 30-35% of those who have recovered.

Photo: Agency

“Moscow” / A. Nikerichev

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