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Explanation of analyzes

PCR analysis - advantages, decoding and description of the method

For the first time about the analysis by a method PTSR have started talking in 1983. This technique was developed by Carey Myullis and his laboratory staff. Since then, the popularity of research has been steadily increasing, because it has a significant number of advantages over other methods.

To date, PCR diagnosis is the standard or standard in identifying infections and pathogens, especially those that are asymptomatic. First of all, this is preclinical diagnosis.


PCR analysis, what is it?

PCR analysis, what is it?

Carrying out the analysis in a PCR machine

The essence of PCR analysis lies in the fact that nucleic acids (DNA or RNA) sequences that are characteristic of a particular type of pathogen are cloned (repeatedly) in vitro.

The abbreviation PCR stands for polymerase chain reaction.

The main distinguishing feature of this method is amplification, i.e. Creation of a huge number of copies of the necessary gene or its fragment. All this is done outside the body, i.e. in vitro.

So, if 20 cycles of PCR are performed, then approximately 1 million copies or more are obtained. This allows you to detect the infection even with its small amount in the source material, when other methods of analysis are powerless. This determines the high sensitivity of this method.

In simple words, you can draw such an analogy - you will not notice one small grain of sand on the floor, but after increasing the number of grains a million times (carrying out PCR), a pile of sand will already be clearly visible.

Advantages of PCR diagnostics

Advantages of PCR diagnostics

The main advantages of the analysis for PCR infection are:

  • и специфичность в сравнении с другими методами, используемыми для выявления инфекционных агентов; the highest sensitivity and specificity in comparison with other methods used to detect infectious agents;
  • the possibility of identifying microorganisms in a variety of biological materials (blood, urine, vaginal secretions, saliva, etc.);
  • the ability to identify several causative microorganisms at the same time, if any. For comparison, the use of bacteriological methods does not allow such a possibility; It is necessary to use various media for the cultivation of various pathogens;
  • The possibility of transporting biological material, because to identify the pathogen, it is not necessary to keep it alive;
  • speed of the analysis;
  • the accuracy of the etiological diagnosis;
  • the possibility of quantitative determination of pathogens - is especially important for conditionally pathogenic microbes, which only after reaching a certain concentration are capable of causing the disease;
  • ability to control the course of the infection process during treatment.

PCR analysis for infection

At present, most of the sexual (and other) infectious diseases are determined by the polymerase chain reaction method. Diagnosis has become widespread due to its high sensitivity and specificity.

Particularly popular is the analysis of PCR on chlamydia.

PCR analysis for chlamydia This is due to the fact that these microorganisms live intracellularly, which creates certain difficulties in their detection.

PCR diagnostics can detect even a minimal amount of chlamydia, which, as a rule, do not yet lead to the appearance of clinical symptoms. Even the presence of only 2 molecules of nucleic acids in the material under study makes it possible to identify the causative infection.

And this is the key to successful treatment, which begins at the preclinical stage.

The following infections are also identified:

  • HIV;
  • viral hepatitis;
  • tuberculosis;
  • tick-borne encephalitis;
  • various venereal diseases, etc.

PCR-diagnostics allows solving a number of other important tasks:

  • Monitoring of therapy and evaluation of its effectiveness;
  • definition of "load by viruses", on the basis of which an individual selection of the dose is made;
  • detection of strains of microorganisms that differ in pharmacological resistance (insensitivity to medicinal products).

Preparation for the analysis

Purposefully prepare for delivery of the analysis, which will be carried out by PCR, is not required. However, it is very important that the specialist take the material for collection in compliance with all necessary conditions for sterility.

So, for example, for taking blood, special vacuum systems should be used, special tubes must be used to take the secret of the genital organs, etc.

In some cases, the material should be transported to the laboratory. To do this correctly, it is necessary to seal the container with biological material sealed. This will prevent the penetration of other microorganisms inhabiting the external environment.

Decoding the PCR result

The results of PCR analysis can be of two variants:

  • positive - the pathogen is detected;
  • negative - the causative agent is not detected.

It is necessary to know - even in the absence of clinical symptoms, a positive result can be obtained.

Decoding the PCR result In this case, it is necessary to focus on the polymerase reaction data, since it allows to identify the disease at the preclinical stage.

Sometimes a dubious answer can be obtained, when the number of detected copies corresponds to the upper limit of the norm. To clarify the cause of the disease, it is necessary to repeat the analysis, paying special attention to the conditions for collecting biological material.

How accurate is PCR diagnosis?

The main advantages of PCR diagnostics can be formulated in the form of several theses:

  • the possibility of obtaining a huge number of copies of pathogenic microorganisms;
  • a large number of copies is the key to successful sequencing (detection).

This provides high accuracy of PCR analysis for detection of intracellular pathogens and slow growing microorganisms.

Therefore, the method is especially informative for the detection of tuberculous mycobacteria and other similar infectious agents. He has the highest accuracy and does not need to recheck the results (except for casuistic cases).

To obtain the most reliable results, it is necessary to fulfill two basic conditions that prevent exogenous (external) infection:

  • correct fence material;
  • correct transportation.

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