Polymerase chain reaction (PCR) is a modern tool for diagnosing various infections, which is highly accurate. PCR analysis allows you to determine the causative agents of infectious diseases based on their genetic material (RNA or DNA). The biological material for the study can be blood, a swab from the genital organs, saliva, and so on.

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The PCR method was discovered in 1983. Its creator, Cary Mullis (USA), received the Nobel Prize in Chemistry for this discovery. Already in the first ten years, the technique has become an obligatory laboratory research all over the world, having received the recognition of scientists and doctors.

Diana Medical Center offers to conduct a study using the polymerase chain reaction method in the shortest possible time and with the highest level of accuracy. Our diagnostic base meets all international standards and requirements.

What infections can be diagnosed by PCR

Send for diagnostics, or. BUTPCR analysismakes it possible to diagnose a wide variety of infections. This group also includes latent, asymptomatic diseases that are in the incubation period:

By using PCR methodcan be found:

• hepatitis C, B;
• ureaplasmosis of the genital organs;
• - ureaplasmosis, trichomoniasis, gardnerellosis;
• chlamydia of the genital organs and respiratory tract;
• bacterial vaginosis;
• Infectious mononucleosis;
• tuberculosis;
• salmonellosis;
• tuberculosis (pulmonary and extrapulmonary forms);
• listeriosis, tick-borne encephalitis, Lyme disease;
• , papillomavirus, ;
• childhood infectious diseases detected during pregnancy and before conception - mumps, diphtheria, measles;
• HIV.

For each of the above diseases, detected by another method, it is advisable to do a PCR study. The causative agents of many infections have several types (strains), and more accurate diagnosis makes treatment more effective. Since different types of pathogens have their own ways of transmitting infection, accurately identifying the pathogen helps protect others from infecting others. For example, hepatitis A can be contracted through shared objects and utensils (dirty hands disease), while hepatitis C can only be contracted through blood, medical instruments, and sexual contact. This is important for those who are close to the patient.

The essence of the polymerase chain reaction method

The method is based on the identification of the pathogen by sections of DNA or RNA. PCR is reminiscent of forensics, when a criminal is found by pieces of skin or hair left at the crime scene. Because every living organism has a unique DNA or RNA structure. The method allows you to accurately identify the microorganism, even if it is present in the test material in minimal quantities.

ORC is suitable for detecting latent carriage, atypical, obliterated and other forms of infectious diseases. Diagnostics is highly accurate, so it practically does not give errors and false results. The analysis is often prescribed as an additional examination to identify a specific type of virus or microbe.

Advantages and disadvantages of the PCR method

PCR analysis is an effective diagnostic tool that allows the doctor not only to correctly determine the type of infectious agent in the patient's body, but also the number of microbes. This feature allows the PCR method to effectively detect chronic infections, such as viral hepatitis.

The advantages of the technique are in the following features:

• Versatility . The method makes it possible to determine all currently known microorganisms, regardless of the type of material under study.
• Specificity . PCR allows you to determine the DNA of a virus or bacteria with 100% accuracy, which does not give any other diagnostic method.
• Sensitivity - even one smallest "piece" of DNA or RNA can be detected and identified, thanks to the rapid reaction of copy formation.
• Efficiency - it is possible to make a diagnosis based on the polymerase chain reaction within a few hours after the sampling of biological material, which makes it possible to start treating the disease in a timely manner.
• Possibility of quantitative analysis . This feature is important in identifying diseases caused by opportunistic flora (for example, thrush). The increased content of Candida fungi in the body causes disease, and the normal amount is up to 10 3 - 104 CFU / tamp. - No.

The disadvantages of PCR diagnostics are the need for high-tech equipment and highly qualified specialists. For analysis, a special laminar box is needed, where the required temperature is maintained and the purity of the experiment is ensured.

How to pass a PCR test correctly: preparation

To understand exactly how to prepare for the upcoming PCR analysis, the patient must definitely check with his doctor what kind of biological material is planned to be taken. Preparation directly depends on this.

• Discharge from the genital organs, a smear from the cervix or urethra, urine - by examining these material options by PCR, genital infections are effectively diagnosed.
• Viral hepatitis C, HIV infection require blood sampling for PCR analysis.
• A throat swab can confirm or disprove the presence of infectious mononucleosis.

Pap smear in women

For the diagnosis of genital infections by PCR in women, as a rule, they take vaginal smear. During pregnancy, the standard rules for preparing for PCR analysis apply.

• A couple of days before the PCR, you need to give up douching, intimate hygiene products.
• A week before the infection test, you should stop using any kind of medication, of course, if they are not included in the PCR test preparation program prescribed by the doctor.
• A couple of days before the examination, you need to begin to refrain from sexual intercourse.
• Washing on the day of the PCR analysis is not necessary, genital hygiene is carried out the night before, only warm water is used.
• A couple of hours before the test, you can not urinate.

Pap smear in men

It is not difficult to prepare for taking a smear from the urethra for PCR. It is enough to follow the rules below.

• 2 days before the PCR examination, you need to start abstaining from sexual relations.
• Medications are stopped approximately 7 days before the test, unless, of course, they have been specifically prescribed by the doctor.
• Hygiene of the genital organs should be carried out the night before; on the day of the PCR analysis, this should not be done.
• It is recommended not to urinate for about 2-3 hours before taking the test.

Blood analysis

If during the PCR analysis the patient's blood becomes the object of study, the rules for preparing for it are as follows.

• The optimal time for donating blood is in the morning, the analysis must be taken on an empty stomach (at least 8 hours without food). Water can be drunk freely.
• Refusal of alcohol a day before PCR analysis, smoking cessation an hour before it.
• If health allows this option, it is recommended to stop taking medicines for a while.
• Before taking blood samples, it is mandatory to rest for about 20 minutes.
• On the eve of the PCR study, emotional and physical overloads are completely excluded, they can affect the results of the analysis.

How is the PCR test performed?

For research, any environment is taken in which the pathogen can be located, but the most commonly used are:

• Blood serum or plasma - to detect a variety of pathogens - hepatitis B, C, D, G viruses, herpes, HIV, cytomegalovirus;
• Urine and prostate juice - in the diagnosis of STDs;
• Sputum, pleural fluid, bronchoalveolar lavage - for the diagnosis of pulmonary and extrapulmonary forms of tuberculosis;
• cerebrospinal fluid - for the diagnosis of infections of the nervous system;
• amniotic fluid - to determine intrauterine infections;
• Throat swab - to identify pathogens of infectious mononucleosis and diphtheria;
  scrapings and smears from mucous membranes for the diagnosis of STDs;
  cells of the gastric mucosa and gastric juice - to identify the bacterium Helicobacter, which causes gastritis and ulcers.

With one taking of the material, you can detect several pathogens that have entered the body at once. Such versatility saves the patient from additional examinations and unnecessary expenses.

It is possible to detect and identify areas of genetic information using special reference DNA markers (primers) created for each known pathogen. The standard allows you to find "your" fragment among millions of others. If this happens, the polymerase chain reaction is triggered.

The PCR reaction makes a huge number of copies of the identified piece of gene information (replication). It is important that only the sections of DNA and RNA necessary for analysis are replicated. Therefore, the purity of the experiment and the ability of personnel to handle equipment and samples are so important.

The chain reaction proceeds very quickly, within two hours the DNA section increases millions of times, which makes it possible to detect and accurately identify the infection. To work with standards, test tubes are placed in a special device. Using the program, an algorithm is set that changes the temperature of the medium several times and affects the course of the reaction. The result of PCR is visible immediately after the end of the study.

How to decipher PCR analysis

Conducting a PCR study allows not only to establish the type of infection present in the patient's body, but also to evaluate it from a quantitative point of view (the number of microbes). Deciphering the results of quantitative PCR analysis plays an important role in detecting and verifying the effectiveness of the treatment of a large number of chronic diseases, say hepatitis C.

The result of the PCR analysis can be positive and negative answers.

• Negative result . Traces of infection were not detected in the biological material, which was the object of study during the PCR analysis. As a rule, on the basis of a negative result, it can be assumed that there is indeed no infection in the body.
• Positive result. This result of the PCR analysis indicates that traces of an infectious disease are present in the biological material of the patient. A positive PCR test result is characterized by a high degree of accuracy.

Sometimes infection is detected against the background of complete health and the absence of signs of the disease. Some patients believe that the analysis was done incorrectly, but the real situation is different. If PCR showed that there is a pathogen in the body, then it really is there. It's just that infectious diseases never start immediately after infection, having incubation periods of varying lengths.

The latent period can last a very long time, for example, with AIDS - several years, until some mechanisms push the viruses to multiply. The causative agent is determined in the body of carriers and those who have not recovered. Very often, various STDs go into a latent (latent) form. In this case, additional laboratory diagnostics may be needed.

Accuracy of interpretation of PCR analysis results

The PCR method, which allows to detect a sufficiently large number of infections, is characterized by increased accuracy, sensitivity and specificity. These characteristics indicate that using the PCR study, you can:

• As accurately as possible to establish the absence or presence of an infectious agent.
• Determine the specific type of infectious agent as accurately as possible (specificity).
• Detect infection even if it is latent. We are talking about a low level of presence of microbial DNA in the patient's biological material under study (sensitivity).

The advantage of the PCR method over enzyme immunoassay and other immunological tools for detecting infection is that it is less likely to give erroneous results. That is, the decoding of the PCR analysis much less often shows the absence of infectious microbes, if they are in the patient's body.

In addition, it almost never happens that the decoding of the analysis reveals the presence of a non-existent infection in the body, that is, it gives false positive results. Of course, PCR results cannot be called absolutely correct, so it is necessary to supplement this study with other methods.

Diagnosis of infectious diseases of various types - both viral and bacterial - is aimed at identifying pathogens at an early stage, which makes it possible to prescribe timely and especially effective treatment. The most modern method for detecting infections is PCR, which stands for polymerase chain reaction. What is the essence of this method and what is its purpose?

The essence of the polymerase reaction

The structure of any virus and microorganism contains RNA or DNA molecules. It is characteristic that these compounds are unique for each, and therefore, by isolating nucleic acids in a blood test in adults or children, a diagnosis can be made with absolute accuracy.

Unfortunately, the concentration of DNA, both in blood samples and in other biological materials, is quite low, so it cannot be determined by ordinary diagnostic methods. In order to cope with this problem, the polymerase chain reaction was invented at one time.

So, the essence of this analysis lies in the specific processing of the blood sample, due to which the concentration of DNA molecules in it increases, and the establishment of their type in the future makes it possible to identify the type of pathogen, as well as to make the correct diagnosis.

How is a PCR blood test performed?

The PCR method is carried out only in laboratory conditions. To carry it out, special enzymes are used that increase the structure of the patient's RNA and DNA several times. In this case, such a number of them should be formed to make it possible to conduct a visual study. During the survey, a copy of such a site is carried out, which fits the required conditions in all respects. What is a PCR blood test for RNA is interesting to many.

The laboratory has the necessary database available, which indicates the exact structure of various infectious agents. Using the PCR method allows not only to establish the type of pathogen, but also to calculate its quantitative proportion.

PCR diagnostics also includes some innovations, among which the following stand out:

Connection of various fragments of DNA;

Introduction of mutation;

Establishing paternity, etc.

What diseases are detected by PCR?

Thanks to PCR, it is possible to identify almost all bacterial and viral pathologies. For research, not only blood can be used, but also other biological materials, such as smears from the urethra and from the uterine cervix, saliva, semen. The analysis becomes quite informative when the causative agent of a certain disease enters the human blood. That is why a blood test for PCR is prescribed for the following pathologies:

Viral hepatitis types A, B, C, D and TT;

Infection of a herpetic nature (that is, viruses of the first, second and fourth types);

Cytomegalovirus;

Enteroviral infection;

HIV infection;

Rubella;

Listeriosis;

Shingles;

Infectious mononucleosis;

Toxoplasmosis.

If we take into account the implementation of PCR using other biomaterials, then the following should be added to the list of pathologies that can be detected using this method:

salmonellosis;

Diphtheria;

Gardnerellosis;

Mycoplasmosis;

Tuberculosis;

Trichomoniasis;

- papillomavirus infection (about a hundred different strains of the human papillomavirus).

Of particular relevance has now become a PCR blood test during pregnancy for TORCH infections, which include toxoplasmosis, cytomegalovirus, herpes infection and rubella. This is due to the fact that the above diseases can cause abnormalities in the development of the fetus.

Advantages of PCR

What are the advantages of this method?

• One hundred percent accuracy of diagnosis: if there are at least several DNA fragments of the pathogen in the blood, they will be determined by the PCR reaction, which means that the correct diagnosis will be made. This is the main difference between this method and other diagnostic methods - a complete blood count, ELISA and others.
• Specificity. During the PCR blood test for borreliosis, for example, there is no such thing as a false negative or false positive result, which distinguishes it from enzyme immunoassay, or ELISA.
• The analysis can be carried out in order to determine several pathogens at once based on a single biomaterial sample, making this method convenient for the patient, because he does not have to take the analysis several times.
• Rapidity. There is no need to isolate and grow the pathogen on special nutrient media, which is necessary during bacteriological examination. You can get the finished result on the day of the analysis.

• By means of a PCR blood test for hepatitis, for example, a hidden causative agent of the disease in the body is determined when the patient acts as a carrier of the infection (HIV or hepatitis).
• Affordable price. The cost of PCR analysis to determine one pathogen ranges from two hundred and fifty to five hundred rubles. A semi-quantitative examination for viruses costs a little more - about a thousand rubles.

Disadvantages of the method

PCR is a high-tech research method that places high demands on laboratory equipment. The room for analysis must necessarily have a biological filter, since there are always particles of saliva and skin in the air, which contain DNA molecules. Failure to comply with the technical requirements for working with biomaterials can lead to misdiagnosis.

Who should take a blood test for PCR?

Anyone can take the survey. The indication for it is the suspicion of sexually transmitted infections (HIV infection, bacterial vaginosis, chlamydia). If unprotected sexual contact accidentally occurred, only PCR will make it possible to make a correct diagnosis at an early stage, if a person has become infected with a particular disease.

Blood for the TORCH-complex is mandatory for pregnant women, as well as those who are just planning to conceive a child.

Although PCR is the most effective diagnostic method, it is not necessary to dwell on it alone. It is necessary to examine the patient in the presence of any pathology comprehensively. If the polymerase chain reaction makes it possible to determine the pathogen, then thanks to a serological study, it is possible to assess the level of effectiveness of therapy, the reaction of the human body to the pathogen and medications. A PCR blood test for HIV should be ordered by a doctor.

Features of the procedure and preparation

Patients who are examined using the PCR technique receive the most reliable result. It must be said that in this case the probability of errors is almost completely eliminated. The results of this analysis are also prepared quite quickly, which makes it easier to determine the diagnosis and it becomes possible to timely prescribe the necessary medical procedures.

The reliability of the result obtained by the PCR method is determined by the correct delivery of biological material for examination. It should not be contaminated with anything, otherwise the result will not be objective.

• a ban on sexual intercourse a day before the procedure;
• a blood test to detect infections should be taken in the morning and only on an empty stomach;
• urine is also given in the morning in a sterile container.

One and a half or two days after the procedure, the PCR blood test will be decoded and the result is ready. There are even cases when you can get the result on the same day.

How to prepare material for analysis?

In order to conduct the study as successfully as possible, it is necessary to correctly take the material from the patient and conduct its competent preparation. It is a well-known fact that in a laboratory study a large number of errors (up to approximately seventy percent) occur during sample preparation.

Currently, in some laboratories, blood is taken using vacuum systems. On the one hand, they minimally injure the patient, on the other hand, they make it possible to take the material so that it does not come into contact with either the environment or the personnel. This avoids contamination of the biological material and maximizes the reliability of the analysis.

Deciphering the results

The result of a blood test for PCR can be positive or negative. If the blood test is negative, then this indicates the absence of infectious pathogens in the material handed over by the patient. A positive analysis confirms that there are infectious agents in the blood, which means that the most effective and high-quality treatment of the patient is required.

The result obtained can be positive even in the absence of any symptoms of the disease. This indicates either the beginning of the pathological process, or that the person is a carrier. If the latter is detected, no medical procedures are required. In this case, the patient is recommended to be constantly monitored by a doctor, which implies, for example, a periodic PCR blood test for herpes and other infections.

Most often they are found in the urethra, in scrapings made from the cervical canal, in saliva. However, it must be remembered that a sick person is able to infect perfectly healthy people, even if he is not bothered by this disease. It may become chronic. It must be said that with a positive result obtained using PCR, it is necessary to prescribe appropriate medical procedures.

Quantitative characterization of PCR

A PCR blood test for infections is also characterized quantitatively. Such a result can only be assessed by a specialist, since it is individual for various infections. It is the quantitative characteristic that allows the doctor to determine the degree of activity of such a pathological process, to determine the exact stage of development of a particular disease.

The study of the results obtained will help the specialist choose the appropriate drug, specify the required dosage.

Diagnostic accuracy

There are three most important characteristics of PCR, namely:

Sensitivity;

Specificity;

Accuracy.

Diagnosis of infections using PCR is characterized by a high probability of detecting infectious agents in the body. Analysis of blood and other fluids is highly specific. Thanks to him, you can easily determine a specific infectious process by passing, for example, a PCR blood test for hepatitis or HIV. Also, PCR diagnostics is highly sensitive. If there is a minimum number of infectious agents in the test material, the PCR method will always be positive.

In very rare cases, a false positive result can be obtained. In the absence of infection, it will, accordingly, be negative.

Identification of hidden diseases

If a person is suspected of having an STI, a blood test is prescribed to determine hidden infections. Any diseases of the genital area can only be determined by examining the patient.

The following diseases can have a latent nature of the course:

• ureaplasmosis;
• chlamydia;
• mycoplasmosis;
• herpes;
• gonorrhea;
• gardnerellosis.

These infections are quite common and very insidious. At the beginning of the disease, they do not have well-defined symptoms, so patients do not go to a specialist. The results of a timely PCR blood test for chlamydia, borreliosis and other infections will help the doctor prescribe an effective treatment.

STIs adversely affect the reproductive system. They can cause infertility or the appearance of defects in the fetus. That is why it is important to take a PCR test before planning a pregnancy.

PCR (polymerase chain reaction) is an achievement of molecular biology, one of the main methods of clinical laboratory diagnostics of the late 20th and early 21st centuries, bringing great benefits in various fields of medical science.

Thus, even if among the millions of cells of the human body it is not the living virus itself that is lost, but only a particle of its DNA, then PCR, if nothing interferes with it, will probably cope with the task and report the stay of the “stranger” with a positive result. This is the essence of PCR and its main advantage.

Advantages and disadvantages

The laboratory performing PCR diagnostics is subject to the highest requirements in terms of equipment, test systems and qualifications of medical personnel. This is a high-tech laboratory that has an arsenal of highly sensitive and highly specific reagents, so it has no particular drawbacks. Unless it gives a positive result in the absence of clinical manifestations, and thus puts the clinician in front of a dilemma: is it worth starting treatment or not?

The doctor observing the patient begins to doubt the reliability of the test results, since he does not see any signs of the disease. But still, given the high sensitivity of the PCR system, it should be remembered that it detects the pathogen even in the preclinical stage, and a positive result in this case is more of an advantage than a disadvantage. Based on this, the attending physician must himself decide on the appropriateness of therapy, taking into account other arguments for and against.

The advantages of diagnostics using the polymerase chain reaction are obvious:

• High specificity, reaching 100%, due to the presence in the selected sample of nucleic acid particles inherent in a particular organism, but alien to humans;
• High performance, after all, PCR is a high-tech automated technique that provides the opportunity to conduct testing on the day of material sampling and thus rid the patient of unnecessary worries;
• PCR, working on a single sample, is able to conduct several studies and about detect multiple pathogens if she has such a task. For example, when diagnosing a chlamydial infection, where PCR is one of the main methods, along with chlamydia, Neisseria (gonococcus) can also be detected - the pathogen. Moreover, this does not negatively affect the reliability of the results;
• PCR testing shows dangerous microorganisms in the incubation period, when they have not yet had time to cause tangible harm to the body, that is, early diagnosis warns of the impending development of the pathological process, which makes it possible to prepare for it and take it fully armed.

In addition, in order to avoid misunderstandings that sometimes arise during diagnostics, PCR also protects itself by the fact that its results can be recorded (photograph, computer) in order to use them for expert purposes, if necessary.

The norm in PCR responses is considered a negative result., indicating the absence of fragments of foreign nucleic acids, a positive response will indicate the presence of an infection in the body, digital values ​​​​indicate the state of the virus and its concentration at the time of testing. However, a complete transcript of the analysis is carried out by a doctor who has undergone special training on the topic "PCR". Trying to interpret the results yourself does not make any sense, since it is possible, which is likely to happen, to misunderstand and begin to worry in advance.

What is PCR “afraid”, what can it do and how to prepare for it?

As with any other study, sometimes test results are false positive or false negative where PCR is no exception. This can happen in the following cases:

1. Violations of the technological process at one of the stages of the reaction;
2. Failure to comply with the rules for the collection of material, its storage or transportation;
3. The presence of foreign impurities in the material.

This suggests that PCR - the diagnosis of infections must be approached carefully, carefully and accurately, otherwise the material samples may change their structural structure or even collapse.

Stages of PCR diagnostics. False results can give violations at any stage of the study

PCR diagnostics of infections belongs to the category of "gold standards" among other laboratory methods, so it can be used to search for pathogens of many diseases that at first glance have nothing in common with each other:

• Tuberculosis of various localization, pneumonia (including atypical, caused by chlamydia);
• Childhood infections (measles rubella, parotitis, measles);
• Diphtheria;
• salmonellosis;
• Zoonotic infectious disease - listeriosis (the disease is characterized by a variety of symptoms with damage to the lymph nodes, central nervous system, internal organs);
• Diseases caused by the penetration of the Epstein-Barr virus (infectious mononucleosis, etc.);
• Oncological pathology provoked by papillomavirus infection (HPV and its types);
• Borreliosis (Lyme disease, tick-borne encephalitis);
• Helicobacter pylori infection, the causative agent of which is the bacterium Helicobacter pylori living in the human stomach. It has been proven that Helicobacter causes the development of stomach or duodenal cancer;
• and practically everything.

PCR diagnostics of sexually transmitted infections is of particular importance, since diseases caused in this way often proceed without any clinical manifestations for a long time, but during pregnancy they begin to become more active and, thus, threaten the health and even life of the child. And behave similarly. Some of them ("torch") are simultaneously related to STIs, so the latter require more detailed consideration. The reader will be able to get acquainted with the most popular methods in the following sections of the article.

How to properly prepare in order to get a reliable result?

We note right away that the preparation for PCR is quite simple, requiring no special efforts on the part of the patient. You just need to complete three simple tasks:

1. Do not have sexual intercourse 24 hours before taking the test;
2. To take and analyze blood from a vein, you need to come on an empty stomach, by the way, you can’t drink either;
3. Urine should be passed at night (in the morning - in a sterile jar purchased the day before at the pharmacy).

PCR can work in any biological environment

The PCR method is not "bloodthirsty", therefore it accepts any biological environment containing a suspected infectious agent. Usually the choice - what you need to take for research, remains with the doctor.

Thus, in search of a pathogen, in addition to a blood test (although it is also suitable and in most cases taken in parallel with other material), you can use:

• (discharge of the urogenital tract);
• Scraping of the mucous membranes of the oral cavity, conjunctiva, nasopharynx, genital tract (in women they are taken from the cervix and vagina, in men - from the urethra);
• saliva;
• semen;
• prostate juice;
• Placental tissues and amniotic fluid (amniotic fluid);
• Urine sediment (after centrifugation), for example, to detect certain STIs and Mycobacterium tuberculosis;
• Sputum and pleural fluid for the same purpose;
• exudates;
• Cerebrospinal fluid in case of suspected infectious lesion of the central nervous system;
• Biopsy material (biopsy) taken from the liver, duodenum, stomach, etc.

I would like to add to the above that in all cases, even in scrapings and secretions, there will be enough material for testing, since PCR testing does not require large volumes, a few microliters are enough for analysis, which are usually taken into an Eppendorf type microtube and sent to study.

Diseases and use of PCR

HIV and the polymerase chain reaction

Usually, when passing an anonymous examination in the case of positive results of immunoblotting, the diagnosis is repeated again. If the diagnosis is confirmed, the patient is prescribed additional studies:

1. Determining, using immunological reactions, the absolute values ​​of the number of CD 4 lymphocytes (immunocompetent cells - T-helpers or helpers), which the infection infects in the first place, after which they lose their basic properties and cannot distinguish between "own" and someone else's. They take the RNA of the virus circulating in the blood plasma for normal cells of the body and do not react to them;
2. Detection of viral RNA by PCR and calculation of the concentration of viral particles in order to establish the stage, severity of the pathological process and prognosis based on these data. Of course, the word "norm" in this regard does not exist, since the reaction is always positive, and the decoding of digital values ​​​​is within the competence of the doctor.

PCR and hepatitis

The PCR method can detect pathogens, most often the test is used to diagnose hepatitis C, which is poorly detected by other methods.

The hepatitis C virus (RNA-containing) in its behavior in the human body resembles HIV. Wedging into the genome of liver cells (hepatocytes), he stays there waiting in the wings, which can come at least 2 years later, at least 20 years later, so doctors called him "gentle killer." Hepatitis C leads to the formation of a malignant process in the hepatic parenchyma, which manifests itself in the later stages. The immune system does not notice all these events, mistaking the virus for a hepatocyte. True, antibodies to the virus are produced in some quantities, but they do not provide a decent immune response. For diagnosing hepatitis C, ELISA is not very informative, since it indicates that the virus has left traces, and it is not known whether it left itself. With HCV, cases of self-healing are known, while antibodies against the virus remain and continue to circulate for life (immunological memory). PCR is noticeably ahead of the formation of antibodies and can detect a viral particle as early as 1-1.5 weeks, while antibodies can appear in the range from 2 months to six months

PCR diagnostics in case of suspected rampant hepatitis C virus in the human body is the most optimal research method, because only it is able to recognize the presence of a "gentle enemy" in the patient's blood or liver biopsy.

However, sometimes there are cases when AT are positive, and the PCR result is negative. This sometimes happens when the amount of virus is very low or when it is dormant in the liver without entering the bloodstream. In order to still find the truth, the patient is re-analyzed, or even more than one.

Papillomavirus infection

If self-healing does not occur, it can also, without showing itself, persist for a long time in the host's body, which does not even suspect it, since PCR has not been done, and there were no symptoms of the disease. However, the presence of papillomavirus infection, albeit latent, is far from being indifferent to human health, where certain types of the virus that cause oncological diseases are of particular danger (types 16, 18).

More often, the female half of the population suffers from HPV, since the virus loves the female genital area more, and especially the cervix, where some types of viruses contribute to the development of dysplastic processes, and then cervical cancer, if dysplasia is not treated and the virus is released. So, the polymerase chain reaction will detect viral DNA, and then indicate the “bad” or “good” (oncogenic or non-oncogenic) type settled in the woman’s body.

Other STIs and TORCH infections

Obviously, the polymerase chain reaction can find any foreign structure consisting of nucleic acids, so this test is suitable for detecting all STDs and TORCH infections, however, it is not always used. Why, say, conduct such expensive research to detect or gonococcus, if there are more affordable and cheaper ones?

TORCH infections and STIs are so interrelated that it is sometimes difficult to determine which group a particular pathogen should be assigned to. In general, it can be difficult to understand them, since these are quite diverse groups of microorganisms that can always be sexually transmitted or only under certain conditions (immunodeficiency), and may be of interest only during pregnancy, due to the possible negative impact on its course and on the fetus.

PCR is the main method for detecting latent infections

The development of clinical manifestations is based on various pathogens, which can only be found by PCR, which is its main task, sometimes together with ELISA, and sometimes as the only confirmatory test, especially if there are no symptoms of the disease. Such a difficult situation can be created by a polymicrobial infection, which, in addition to obvious pathogens, also includes opportunistic pathogens.

Ureaplasma is often seen in tandem with mycoplasma. And this is no accident. These species, like chlamydia, are neither viruses nor bacteria, they live inside cells and belong to STIs, although their presence in a healthy body is also far from uncommon. So, in order to distinguish a healthy carrier from a sick person, special methods are needed, where PCR is considered the most reliable, since, due to the peculiarities of the structure and behavior of these microorganisms, other studies are ineffective.

As for (type 1, 2) and, which also belongs to herpes viruses (type 5), the situation here is also ambiguous. The infection rate of the world's population is approaching 100%, therefore, in this case, the identification of the virus and its dose are very important, which is especially important during pregnancy, because for an adult, the virus that has taken root in his body often does not cause any trouble and does not give signs of disease.

Therefore, such an examination prescribed by a doctor should not be ignored, because in some cases the polymerase chain reaction is an obligatory and necessary method of laboratory diagnostics that can protect not only a woman, but also a small, unborn man from serious complications.

In conclusion, I would like to note that such a wonderful method as PCR has been serving humanity for more than 30 years. At the same time, the tasks of the test are not limited to the search for pathogens of infectious diseases. The polymerase chain reaction, born on the soil of molecular biology, is inextricably linked with genetics, it successfully used in forensics for personal identification, in forensic medicine to establish paternity, in veterinary medicine, if the animal clinic has the ability to purchase expensive equipment, as well as in other areas (industry, agriculture, etc.).

Video: PCR - essence and application

PCR analysis, not many people know what it is, although today it is one of the innovative methods for diagnosing infectious diseases, for which its developer received the Nobel Prize in 1993. This high-tech method allows you to detect serious diseases at an early stage and start their treatment in a timely manner.

The analysis is based on the principles of molecular biology. A PCR study consists in using a special enzyme that, under the influence of temperature conditions, copies the RNA and DNA of bacteria and viruses present in the collected biomaterial. Such mass reproduction makes it possible for the doctor to determine exactly what species the bacterium that provoked the disease belongs to, as well as to measure the level of its concentration in the biomaterial. The copying procedure is carried out in a special apparatus - an amplifier, which heats and cools the test tubes with the collected material, creating convenient conditions for replication.

PCR research is carried out for many reasons, but most often it is used to determine the presence of infectious diseases such as:

• herpes;
• genital infections - chlamydia, ureaplasmosis, bacterial vaginosis, trichomoniasis;
• candidiasis;
• hepatitis;
• mononucleosis;
• listeriosis;
• cytomegalovirus;
• tuberculosis;
• human papillomavirus;
• tick-borne encephalitis.

PCR analysis is not limited to the scope in medicine, screening is often done if it is necessary to understand who owns the biological material found at the crime scene, that is, PCR analysis is widely used in forensics. It should be noted that a smear or blood for PCR is taken if paternity is required. The results of PCR diagnostics are in no way inferior to the usual analysis for DNA kinship, and it is much cheaper.

Features of diagnostics

PCR analysis has a huge number of positive aspects. First of all, it is important to note the sensitivity of the test. The PCR analyzer is able to determine the DNA molecules of bacteria even if they are small in number, that is, the doctor receives information about the early stage of the disease or the onset of the chronic form of the disease. A PCR blood test can even determine the presence of an infectious disease, which is in a latent form and does not give itself away.

It should be noted that PCR analysis in men and women can be carried out in the presence of any type of material, it does not have to be blood or a smear, saliva, skin cells and even urine will do.

The results of PCR analyzes can be extensive, since PCR diagnostics of infections can capture several pathogens at once, which are located in one biomaterial sample. The examination can be done at any convenient time, which the analysis shows a person can find out in a short period of time, since the results of the diagnosis of the biomaterial are ready in 5 hours.

All doctors agree that a blood test for PCR or other material never gives false results if the diagnostic methodology is followed correctly. PCR positive or PCR negative can only be false under the condition that the laboratory staff does not have a high level of professionalism. If the removed biomaterial was contaminated or stored incorrectly, then the decoding of the PCR analysis may have distorted results.

Preparation for diagnostics

A PCR smear in women is taken from the cervix if it is necessary to identify sexually transmitted diseases, for example, chlamydia, ureaplasma, or herpes. If PCR is required to be carried out on these bacteria by a man, then a discharge from the urethra is taken from him - prostate juice, in other words. Blood is examined by PCR if they want to determine hepatitis, toxoplasmosis and HIV. A PCR analysis is done for mononucleosis and cytomegalovirus by removing a swab from the throat. Polymerase chain reaction for the presence of pulmonary infections is carried out with the presence of a biomaterial such as sputum or pleural fluid.

PCR during pregnancy is done if there is a suspicion of intrauterine infections, as well as diseases and pathologies of the fetal nervous system. As a biomaterial for research, placental tissue is taken from pregnant tissue. If a person has a lesion of the nervous system, the cerebrospinal fluid is examined. To determine such a bacterium as Helicobacter pylori, biopsies of the stomach and duodenum are used.

Urine analysis PCR is also often used, but it is less preferred than a blood test. It allows you to see the presence of pathogenic microorganisms that provoke infectious diseases, but cannot indicate their exact number and degree of development of the disease. Urine PCR is used if for some reason it is not possible to withdraw blood or make a smear. It should also be noted that urine PCR may be used to investigate infections in young children. Urinalysis also allows you to determine the presence of infection and inflammation in the bladder, determine stones, sand, as well as cystitis and urethritis.

As mentioned above, you can take an analysis for PCR in the presence of any biomaterial. PCR analysis, what it is, you know, you also need to know how to prepare for diagnosis. Preparation directly depends on what is to be withdrawn, for example, you need to pass urine after thorough hygiene of the genital organs in the morning. Blood is donated on an empty stomach, during the donation, or rather, the day before, it is necessary to abandon the use of any medications. If there are chronic ailments, then the list of approved drugs for use is decided individually by the attending doctor.

Fecal analysis is taken in the morning after careful preparation. On the eve of delivery, it is necessary to refuse heavy food and conduct thorough hygiene of the genital organs. Fecal analysis will be unreliable if the biomaterial was removed with an enema, a natural descent of the material is necessary. Preparation for the delivery of saliva is not required, it is enough to stop smoking, drinking citrus juice.

Before submitting biomaterial for the determination of diseases that are transmitted during sex, patients are required to exclude sexual contact two days before PCR diagnosis. Women are not allowed to take a smear from the cervix during critical days two days after menstruation, otherwise the PCR decoding will have distorted information.

Screening results

It is only a qualified doctor who can explain in detail what such a PCR analysis says about the condition of a particular patient, it will not be easy to understand the data indicated in the form on your own. If you ask the doctor to decipher the data, he will first of all say whether the result is positive or negative. If the analysis is negative, then the person is healthy, and no bacteria were found in the test material. In the case of a positive result, the exact type of pathogen and its quantity are indicated, you can also find out the exact period when the infection was by the presence of certain immunoglobulins.

There are several classes of immunoglobulins that can clearly reflect the patient's condition:

1. IgG develop in the blood after 4 weeks of infection and can persist in the blood for up to several years. They are not always indicators of bacteria, sometimes they act as a memory of the body that it once encountered a similar type of pathogen.
2. IgM - appear at the very beginning after infection. As a rule, they are already visible on the 5th day, these are the first defenders of the body that attack the bacterium. They disappear from the blood result after two weeks. If they are present in the blood test, then it can be assumed that the infection occurred quite recently, about a week ago.
3. IgA signals the acute development of a bacterial infection in the body or the recurrent stage of a chronic disease.

There are a number of cases when the analysis shows a positive result, but the person does not feel bad at all. This does not at all indicate an error in the diagnosis, rather, there is a chronic form of the disease, which is in a dormant state, or the development of the disease is just beginning. At this time, there are not enough bacteria that can provoke symptoms.

Now you know the principle of analysis, and you can apply for this diagnosis if there is the least suspicion of an infectious disease. The duration of further treatment and its effectiveness directly depend on how quickly you pass the diagnosis, which is practically painless. In order to constantly maintain your health at a good level, it is recommended to undergo preventive PCR diagnostics once a year for the presence of STDs, as well as infections of other organs. It is better to prevent the disease than to deal with its consequences later.

The polymerase chain reaction has been known for 30 years. It is widely used in many fields, from archeology to genetics.

It is the PCR method that helps to establish paternity, but it is most often used to detect various infectious diseases in the human body.

How is PCR analysis carried out, and what is it? We will try to answer these questions in detail.

PCR analysis - what is it?

Polymerase chain reaction (PCR) is a highly accurate method of molecular genetic diagnostics, which makes it possible to detect various infectious and hereditary diseases in humans, both in the acute and chronic stages, and long before the disease can manifest itself.

The PCR method is absolutely specific and, performed correctly, cannot give a false positive result. That is, if there is no infection, then the analysis will never show that it is. Therefore, now very often, in order to confirm the diagnosis, an additional PCR analysis is taken to determine the pathogen and its nature.

The polymerase chain reaction (PCR) was developed in 1983 by Cary Mullis (USA), for which he was awarded the Nobel Prize in Chemistry in 1993.

What is the advantage of this method?

Diagnosis by this method allows you to find the pathogen directly in the gene contained in the studied materials. This is the most accurate analysis for sexual infections, latent infections, various sexually transmitted diseases.

Differences between PCR diagnostics and other laboratory research methods are as follows:

• the method is aimed at identifying the pathogen itself;
• diagnostics by PCR is versatile: to detect several pathogens;
• diseases, only one biological sample of the patient is sufficient;
• the method is highly sensitive and is not accompanied by other cross-reactions.

In addition, the advantage of PCR diagnostics is that any biological material of the patient is suitable for analysis: blood, secretions from the genital organs, urine, semen.

What infections can be detected by a PCR smear?

A large number of infectious agents may be present in the body, including “hidden” ones that do not manifest themselves for a long time.

PCR smear analysis makes it possible to detect such infections:

• ureplasmosis of the genital organs;
• candidiasis ();
• herpes;
• the presence of cancer cells;
• assess the hormonal state;

The studied material for PCR is usually sputum, saliva, urine, blood. Before carrying out the analysis, it is necessary to carefully prepare for it, having received a preliminary consultation with a doctor.

Blood for PCR is usually donated on an empty stomach. Good results are shown by analysis when the material for research is taken from the cervical canal or urethra. In this case, it is best to carry out PCR diagnostics no later than one day after intercourse.

Varieties of PCR

PCR is used in many areas for analysis and in scientific experiments. There are different analysis methods:

1. reverse transcription PCR(Reverse Transcription PCR, RT-PCR (English)) - used to amplify, isolate or identify a known sequence from an RNA library.
2. Inverted PCR(Inverse PCR (English)) - is used if only a small area within the desired sequence is known. This method is especially useful when it is necessary to determine neighboring sequences after DNA has been inserted into the genome.
3. Nested PCR is used to reduce the number of side products of a reaction. Use two pairs of primers and carry out two consecutive reactions.
4. Asymmetric PCR(English Asymmetric PCR) - is carried out when it is necessary to amplify mainly one of the chains of the original DNA. Used in some sequencing and hybridization analysis techniques.
5. Quantitative PCR(Quantitative PCR, Q-PCR (English)) or real-time PCR - used to directly observe the measurement of the amount of a particular PCR product in each reaction cycle.
6. Stepped PCR (Touchdown PCR (English)) - using this approach, the influence of non-specific binding of primers is reduced.
7. Group-specific PCR(English group-specific PCR) - PCR for related sequences within one or between different species, using conservative primers for these sequences.

If the nucleotide sequence of the template is partially known or not known at all, degenerate primers can be used, the sequence of which contains degenerate positions in which any bases can be located. For example, the primer sequence could be: …ATH… where H is A, T, or C.

What biological materials are being studied?

Various biological media and human fluids can serve as a material for PCR research, in which foreign DNA of a bacterium or DNA or RNA of a virus can be detected:

1. Urine. It can be used for infectious lesions of the genitourinary tract in men and urinary organs in women (in men, the use of urine as a material replaces epithelial scraping).
2. Phlegm. It is used for the diagnosis of tuberculosis and less often for the diagnosis of respiratory forms of chlamydia and mycoplasmosis. Sputum in the amount of 15-20 ml is collected in a sterile (disposable) vial.
3. biological fluids. Prostate juice, pleural, cerebrospinal, amniotic fluid, articular fluid, bronchoalveolar lavage, saliva are taken according to indications.
4. Epithelial scrapings from mucous membranes. Usually used to diagnose sexually transmitted diseases (STDs), such as gonorrhea, chlamydia, mycoplasmosis, ureaplasmosis, trichomoniasis, gardnerellosis, herpetic and other infections that affect the mucous membranes.
5. Biopsies. Most often, biopsy specimens of the stomach and duodenum are used to detect Helicobacter pylori infection.
6. Blood, plasma, serum. Used for PCR analysis of hepatitis B, C, D, G viruses, herpes, CMV, HIV, human genes.

How to prepare for the analysis?

The reliability of the PCR result directly depends on the correctness of the delivery of the material for examination. The material must not be contaminated, otherwise the result of the study will not be objective. The most important recommendations before taking a PCR test include the following requirements:

1. Urine is given in the morning in a sterile container.
2. A blood test for infections must be taken on an empty stomach in the morning.
3. You should not be sexually active the day before the test.

The result of the analysis will be ready in 1.5-2 days after the procedure in question. There are situations when the result can be prepared on the same day.

Deciphering the analysis of the PRP

The process of interpreting the presented study is notable for its simplicity. The results of PCR analysis can be obtained 1.5-2 days after the delivery of the material. In some cases, the result is ready on the first day, and this is what they can mean:

• Negative result shows that the material being diagnosed does not contain the desired infectious agent.
• PCR positive indicates that DNA or RNA of the pathogen is present in the human body.

In some cases, quantitative determination of microorganisms is carried out. This is especially true in diseases caused by opportunistic pathogens. Since these bacteria show their negative effects only when they are in excess.

Also, quantitative PCR analysis is important for the choice of therapeutic tactics and for the purpose of monitoring the treatment of viral infections such as HIV and hepatitis viruses.

How accurate is PCR in diagnosing infections?

The PCR method is characterized by high accuracy, specificity and sensitivity. This means that this analysis is capable of:

• accurately determine the presence or absence of infection;
• specify exactly what kind of infection it is (specificity);
• detect infection even at a very low content of microbial DNA in biological material,
• which has been tested (sensitivity).

PCR analysis: price and terms

The price of a specific analysis will depend on which infection you will be tested for. Approximate prices and terms:

1. STI: 300-500 rubles, terms - 1 day;
2. Epstein-Barr virus, human papillomavirus, herpes, cytomegalovirus: 300-500 rubles, terms - 1 day;
3. Hepatitis A, B, C, D, G: qualitative analysis 650 rubles, quantitative analysis 2000 rubles. Terms - up to 5 days;
4. Antibodies to the hepatitis C virus, total (Anti-HCV) - 420 rubles;
5. Antibodies to the hepatitis C virus, IgM (Anti-HCV IgM) - 420 rubles;
6. Helicobacter pylori (Helicobacter pylori): 300-400 rubles, terms - 1 day;
7. HIV (antibodies and antigens) - 380 rubles;
8. HIV RNA, qualitatively - 3,500 rubles;
9. HIV RNA, quantitatively - 11,000 rubles.

To save money, you can choose a fixed package of analyzes. This service is provided by most clinics where you can take an analysis using the PRC method (in vitro, onclinic, etc.).