What is PCR analysis? PCR analysis: what it is, indications and preparation for the study. Indicators and interpretation of PCR results

In order to quickly and accurately identify the presence of genetic and other diseases in a person, today doctors use PCR diagnostics. This analysis is highly informative and is widely used by specialists in various fields. This study can show the presence of the disease long before symptoms appear. Today, without this analysis, doctors do not make a final diagnosis.

The essence of the method

The method was discovered back in 1983 by an American scientist named Kary Mullis. Later, the scientist was awarded the Nobel Prize for his invention. What is a PCR test? The principle of the method is that in the laboratory, specialists repeatedly increase the number of human DNA fragments. At the same time, the infection molecule increases. Thus, foreign cells become visible under a microscope.

Today, the PCR method is used in various fields. It is he who helps criminologists identify biological material, establish disputed paternity or maternity, helps identify genetic diseases, and indicates the presence or absence of infectious diseases.

What the analysis can detect

PCR techniques are now actively used to detect hidden infections. Thanks to special analysis technology, infection can be detected at the earliest stages, when symptoms are not yet out of the question.

A PCR test can show the presence of the following diseases:

• Oncological diseases.
• Hepatitis of all types and subtypes.
• Ureaplasmosis.
• Salmonellosis.
• Candidiasis.
• Diphtheria.
• Chlamydia.
• Cytomegalovirus.
• Mycoplasmosis.
• Helicobacteriosis.
• Herpes.
• Gonorrhea, etc.

PCR diagnostics of infections is of particular importance for identifying chronic, sluggish and latent infections that do not manifest themselves with specific symptoms. Such a study is often prescribed when planning pregnancy. It is important to examine the blood of not only the expectant mother, but also the father, because many diseases can be inherited.

Benefits of analysis

PCR analysis has a number of undeniable advantages over other types of blood testing for the presence of infections, namely:

• Detection of the causative agent of the disease with high accuracy.
• Elimination of false positive results.
• Possibility of detecting even one pathogen cage.
• The ability to examine biological material to detect several infections simultaneously.
• Quickly receive research results.
• Possibility of detecting infection before clinical manifestations of the disease.

Today the method is constantly being improved. New tests are emerging to detect dangerous viruses and infections. According to statistics, it is this examination that allows you to detect harmful cells long before the appearance of clinical symptoms. This means that the analysis refers to early diagnostic methods, which allows the patient to be treated at the earliest stages of the disease.

Today doctors attach particular importance to this method in detecting cancer cells in the body.

Modern doctors say that the use of polymerase chain reaction PCR in the fight against cancer is the most modern and effective method for diagnosing oncology in the early stages of the disease.

Types of analysis

Today, doctors often suggest doing a comprehensive PCR test. This study is more informative and helps doctors quickly make an accurate diagnosis. An analysis for an individual pathogen is most often carried out to monitor treatment or when a particular disease is suspected, and a comprehensive test helps to identify hidden infections.

The most common comprehensive studies are PCR 6 and PCR 12. The numbers in the name indicate the number of infections for which the biological material is tested. PCR can also be quantitative or qualitative. The first is most often more expensive, because it accurately determines the number of viral cells in biological material, which means it helps to establish the stage of the disease.

Most often, an analysis is prescribed when doctors cannot identify the causative agent of the disease. So, for example, a patient has certain symptoms of a disease, but other tests do not reveal an infection. In this case, the PCR method is simply irreplaceable. Also, research is required before planning a pregnancy. In addition, a blood test is prescribed to detect congenital genetic diseases and according to other doctor’s indications. In addition, a study may be ordered by court order to determine paternity or other indicators at the request of the prosecutor's office.

Material for research

Various human fluids and media can serve as material for research using PCR diagnostics. Most often, the patient's blood, urine, scrapings and mucus are taken for research. The collection of this or that material directly depends on the study for certain infections.

Sexual diseases are determined by smears taken from the genitals, urine or scrapings. To determine the presence of HIV, hepatitis, toxoplasmosis and other infections, doctors need to examine the patient's blood. Sometimes cerebrospinal fluid is taken for analysis, for example, to examine it for infections of the nervous system. And to detect intrauterine infections, it is necessary to take samples of amniotic fluid and placental tissue.

Today, gynecologists advise all women to take a PCR test at the very beginning of pregnancy, if you did not do the test at the planning stage.

This test must be taken before 12 weeks of pregnancy. The material for the study is taken from the cervix. The procedure is safe and does not cause discomfort. The analysis allows us to identify dangerous infections that can affect the intrauterine development of the fetus. This analysis is called PCR-6.

Submission rules and decoding

Every patient should know that the accuracy of the result of any analysis depends on compliance with the rules for submitting biomaterial. The method and rules for taking the analysis are determined by the type of test. If you need to donate blood, you must come to the collection in the morning on an empty stomach. If testing for sexually transmitted infections is necessary, you should observe sexual rest for at least a day before collecting the material. Urine collection also requires compliance with certain rules. Urine should be collected during the first urination in the morning. You need to collect medium urine, before doing this you need to wash and dry with a clean towel. The container must be sterile.

Deciphering the research results is not particularly difficult. In molecular DNA RNA diagnostics using the PCR method, the result can only be positive or negative. On the laboratory form, opposite each infection for which a study was carried out, you can see a “+” or “-” sign. Accordingly, “+” is a positive result, which indicates that traces of this infection were found in the material being studied.

When deciphering the analysis, it is very important to determine the quantitative ratio of virus cells. The presence of an infection cannot always be regarded as a disease. There is such a thing as being a carrier of an infection. This means that a person has infection cells, but he does not suffer from this disease. However, such carriage does not protect against the possibility of infecting other people. It is the quantitative analysis that helps doctors determine whether you are a carrier or a patient, as well as identify the stage of the disease and select effective therapy.

Where to submit

Many patients are interested in where to get a PCR test to get a reliable result? Today you can get tested in any specialized clinic or private medical center. PCR analysis is paid, its price depends on the type of test.

This research is not carried out in district clinics; there is simply no special modern equipment there.

Many people neglect analysis, believing that they do not need this research. However, if the doctor prescribed this test for you, it means that he had certain difficulties in making an accurate diagnosis, and therefore in prescribing effective therapy. In this case, it is better to undergo the study, because it is in your interests.

Also, all young couples who are planning a pregnancy must undergo this examination. A referral for testing can be obtained from a family planning center. Many couples also do not attach due importance to the analysis, believing that if the spouses do not have obvious hereditary diseases, then their baby will be born healthy. However, today there are a lot of hidden infections that can affect the course of pregnancy and the health of the baby.

Today, diagnostic methods can reveal the most hidden infections that can live in the human body for years without manifesting themselves. However, you do not need to take the tests yourself. All studies must be carried out according to the indications of the attending physician, otherwise your life may turn into endless trips to diagnostic centers. First of all, if you have any complaints, you should see a doctor. He will be the one who will be able to assess your condition and prescribe only the tests that are necessary for you.

In contact with

Today, PCR 12 analysis is designed to obtain results in a short period of time. Often, this method is used to identify urogenital infections. In cases where it is necessary to identify hidden infectious diseases that are sexually transmitted, this method of effective diagnosis is used.

It is worth considering its specifics, considering the tests that are carried out along with the diagnosis.

PCR method

With the help of DNA and RNA studies, the PCR diagnostic procedure is based 12. Explanation of the meaning of the term “polymerase chain reaction”. This diagnostic method is considered one of the most modern and accurate studies. It was formulated based on the molecular biological developments of scientists.

Using this method, specialists can detect the causative agent of many diseases.

This happens due to the doubling of individual sections of DNA using artificially created enzymes.

Even a small amount of pathogen molecules is enough to promptly diagnose a pathological change in the human body. PCR 12 is considered a diagnostic method, which is distinguished by its increased sensitivity.

The classification of the method divides PCR 12 into quantitative and qualitative types. By using a high-quality type of diagnostics, it becomes possible to detect pathogenic development in a timely manner. Thanks to the quantitative type of diagnostics, the specialist receives a detailed clinical picture of the patient’s health status. This happens due to the precise determination of the number of aggressive organisms.

PCR 12 involves the use of a number of tests for diseases such as chlamydia, trichomoniasis, mycoplasmosis, ureaplasmosis, or the presence of tuberculosis. A method is used to detect hepatitis C, B, or herpes virus. This method is used to detect candidiasis, infectious mononucleosis, or bacterial vaginosis.

There is a wide range of infectious diseases that can be identified through the use of diagnostics. Comprehensive PCR 12 analysis includes PCR of 12, 13, 15 infectious diseases.

Specialists in various fields actively use this method of diagnosing diseases. Among them are the areas of oncology, hematology, urology, and gastroenterology. The field of medicine, in particular, pulmonology, and the center of physiatry actively use this modern technique.

Another positive thing is that the procedure is short in duration. Within one hour, the genetic material of the pathogenic organism can be identified.

Attention! A quick result can be obtained by eliminating the electrophoresis phase. This helps avoid the possibility of a false positive result.

In general, PCR of 12 infections helps to identify even several pathogens. This has a positive effect on diagnostic efficiency. Until the period when characteristic symptoms appear, using the method, a specialist diagnoses the disease and prescribes a course of treatment. All this affects the reduction in the duration of therapy and the patient’s rapid recovery.

Detection of hidden infections using PCR

Examination of PCR tests on 12 contributes to the effective detection of urogenital infectious diseases. The difficulty of identifying diseases in this area is due to the absence of obvious abnormalities or symptoms.

You can highlight a list of diseases that are sexually transmitted. In particular, these are herpes, chlamydia, gardnerellosis, or mycoplasma, gonorrhea.

Attention! In the case when a person is promiscuous, diseases of this kind pose a threat and are quite common.

The difficulty of their timely detection lies in weak symptoms or their complete absence. Lack of timeliness is fraught with the transition of the disease to a severe stage of development, which poses serious threats to the patient’s life.

In addition to taking blood, it is necessary to take a smear from the area of ​​the cervical and urethral canal of the uterus. Before this procedure, it is important to abstain from sexual intercourse for 24 hours. Douching should not be used.

The preparatory stage when taking PCR 12 is a guarantee that the results obtained as a result of the procedure will be reliable. In this case, you should follow all the recommendations without neglecting any point. This is primarily savings. Not only money, but also your time and effort.

Before taking PCR 12, it is important to follow the following recommendations:

• It is important to adjust your diet, in particular, limit your intake of spicy, salty, fatty and fried foods. Heavy, unhealthy foods should be excluded during the preparatory period;
• If possible, medications should be avoided. If this item cannot be fulfilled for individual reasons, you should warn your doctor about this;
• refrain from drinking alcoholic beverages one week before the procedure. It is worth remembering that you should not smoke a few hours before the test;
• the analysis is carried out in the morning, on an empty stomach. You can drink only water before the examination; at least 10–12 hours must pass since your last meal;
• It is worth remembering that physiological procedures affect the composition of the blood. These procedures should be avoided before testing;
• During this period, try to minimize the impact of stressful situations on your body and excessive physical activity;
• a woman can undergo the study strictly before the start of her critical days, or a few days after their end;
• You should abstain from sexual intercourse one day before the procedure.

If we are talking about a complex procedure, then additional research should be carried out. In particular, PCR for 15 infections requires, in addition to all previous recommendations, to exclude the consumption of yellow vegetables and fruits due to their high carotene content.

Disadvantages of the PCR method

Important! PCR assays 12, 13 are considered to be the most common in application. The type of infection depends on the number of studies required.

conclusions

Experts note the advantages of using PCR diagnostics. The positive side of its use is the speed of obtaining results and their reliability.

Using this method, it becomes possible to determine the presence of not only the disease itself, but also the stage of its development.

Using this method, it is possible to identify any type of virus, in particular, even those that are sexually transmitted.

A number of recommendations should be followed to obtain the most accurate, reliable results. This is simple advice from doctors. Diet, lifestyle, bad habits, or taking medications affect the final test results. In order to avoid mistakes, you should adhere to the basic rules and take a responsible approach to the preparatory stage of this procedure.

Thanks to modern diagnostic methods, specialists are able to identify a wide range of causative agents of various infections, which subsequently guarantees quick and effective treatment of the disease. One of the unique methods for detecting infection in the body is PCR analysis, which allows one to determine not only the type of infectious pathogen, but also its quantitative presence in the body. What is a PCR analysis, and what infections can be determined with its help?

What is a PCR test?

PCR (polymerase chain reaction) analysis is a highly accurate method for identifying various infections. To carry out the PCR analysis, genetic material is used, namely DNA or RNA, which is present in the samples taken for analysis.

To carry out the analysis, depending on the type of disease being determined, biological material of various types can be used, including blood, discharge from the genital organs, a swab from the throat, etc.

The material being studied for PRC analysis is placed in a special reactor, where enzymes are also added that can bind microbial DNA and create its copy. As a result of several cycles of the obtained material, the DNA of the microbe becomes sufficient to determine the causative agent of infection with high accuracy. PCR analysis also makes it possible to evaluate the effectiveness of treatment of many chronic infections.

What diseases can be detected using a PCR infection test?

The PCR infection analysis allows you to diagnose many infections, and the results of the PCR analysis can also determine the degree of spread of the infection, which is very important for the correct prescription of treatment. PCR analysis is prescribed to determine the causative agents of the following diseases:

• hepatitis B and C is detected by detecting the DNA of the corresponding virus in biological material;
• chlamydia, detected by detecting Chlamydia trachomatis DNA;
• ureaplasmosis, detected by detecting DNA from Ureaplasma urealiticum and Ureaplasma parvum;
• mycoplasmosis, detected by detecting DNA from Mycoplasma hominis, Mycoplasma genitalium;
• candidiasis, detected by detecting Candida albicans DNA;
• bacterial vaginosis, detected by detecting Gardnerella vaginalis DNA;
• trichomoniasis, detected by detecting Trichomonas vaginalis DNA;
• infectious mononucleosis, detected by detecting Epshetain-Barr virus DNA;
• tuberculosis, detected by detecting the DNA of Mycobacterium tuberculosis;
• papillomavirus infection, detected by detecting human papillomavirus DNA;
• HIV (AIDS), detected by detecting the DNA of the human immunodeficiency virus;
• herpes infection, detected by detecting the DNA of herpes simplex viruses types 1 and 2;
• Helicobacter pylori infection is detected by detecting Helicobacter pylori DNA.

PCR analysis for hepatitis C

PCR analysis for hepatitis C allows you to accurately determine the presence of the virus in the blood, from which a conclusion is made about the presence of this disease in the patient. Today this is one of the most effective methods for determining hepatitis C. PCR analysis for hepatitis C can be qualitative and quantitative.

A qualitative test for hepatitis C directly indicates the presence of the virus in the patient’s blood. The qualitative result of the PCR analysis in this case can be “detected” or “not detected”. This type of test has a certain sensitivity, ranging from 10-500 IU/ml. This means that if the concentration of the virus in the blood is lower, the result of the qualitative analysis will be “not detected”.

Quantitative PCR analysis for hepatitis C allows you to determine the concentration of the virus in the blood. This indicator is referred to as “viral load”, and it represents the number of units of viral RNA found in a certain volume of blood. The interpretation of the PCR analysis in this case can be expressed in different ways. Some laboratories will indicate, for example, 1.5 million IU/ml, which corresponds to 1,500,000 IU/ml or 1.5 * 106 IU/ml. Other units of change can also be used - copies/ml. You can convert copies to international units (IU) using the formula: 1 IU/ml = 4 copies/ml.

To determine the degree of spread of the virus in the body, the following indicators can be taken. If the transcript of the PCR analysis contains a viral load value of 800 * 10 3 or 800,000 IU/ml, then this indicates a high level of virus in the blood. A load whose value exceeds 1*10 7 ME/ml is considered very high.

PCR analysis for chlamydia

To carry out PCR analysis for chlamydia, biological material is used in the form of scrapings from the urethra, urine sediment, prostate secretion, semen, and scrapings from the conjunctiva. PCR analysis for chlamydia involves a qualitative determination of the presence of the infectious agent in the material. The interpretation of PCR tests for chlamydia may indicate the presence of infection or its absence. A normal chlamydia PCR test result should be negative. A positive result indicates the presence of infection in the acute stage of the disease.

In order for the result of the PCR analysis to be reliable, the study patients are recommended to refrain from using any medications, as well as from using hygiene products that contain bactericidal additives, for 3 days before submitting the biomaterial. In addition, before taking the test, you must refrain from emptying your bladder for 2 hours.

PCR method to protect health

Today, PCR analysis makes it possible to make accurate diagnoses where other tests provide an inaccurate picture of the disease. Today this is the fastest and, most importantly, the most accurate diagnostic method. The good thing about this method is that it allows you to find pathogens of different nature in different biological materials. At the same time, the accuracy of detection does not suffer from the presence of which pathogen is being tested. The transcript of the PCR analysis contains enough information about what kind of infection and in what quantity is present in the body.

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 for what purpose is it carried out?

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 person, 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 in both blood samples and other biological materials is quite low, so it cannot be determined using conventional 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 a blood sample, due to which the concentration of DNA molecules in it increases, and establishing their type in the future makes it possible to identify the type of pathogen, as well as make a 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 so that a visual examination becomes possible. During the survey, a copy is made of an area that meets the required conditions in all respects. What is a PCR blood test for RNA is interesting to many.

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

PCR diagnostics also includes some innovations, including the following:

Connection of various DNA fragments;

Introduction of mutation;

Establishing paternity, etc.

What diseases are detected using PCR?

Thanks to PCR, it is possible to detect 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 cervix, saliva, and sperm. The analysis becomes quite informative when the causative agent of a certain disease enters the human blood. That is why a PCR blood test is prescribed for the following pathologies:

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

Herpes infection (that is, viruses of the first, second and fourth types);

Cytomegalovirus;

Enterovirus 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 identified using this method:

Salmonellosis;

Diphtheria;

Gardnerellosis;

Mycoplasmosis;

Tuberculosis;

Trichomoniasis;

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

PCR blood analysis during pregnancy for TORCH infections, which include toxoplasmosis, cytomegalovirus, herpesvirus infection and rubella, has now become particularly relevant. This is due to the fact that the above diseases can cause abnormalities in the development of the fetus.

Pros of PCR

What are the advantages of this method?

• One hundred percent diagnostic accuracy: if at least several DNA fragments of the pathogen are present in the blood, they will be determined by the PCR reaction, which means the correct diagnosis will be made. This is precisely the main difference between this method and other diagnostic methods - general blood test, ELISA and others.
• Specificity. When performing a PCR blood test for borreliosis, for example, there is no such thing as a false negative or false positive result, which distinguishes it from an enzyme-linked immunosorbent assay, or ELISA.
• The analysis can be carried out to determine several pathogens at once based on one sample of biomaterial, making this method convenient for the patient, because he does not have to be tested 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 directly on the day of the analysis.

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

Disadvantages of the method

PCR is a high-tech research method that places increased demands on laboratory equipment. The room for analysis must necessarily have a biological filter, since the air always contains particles of saliva and skin, which contain DNA molecules. If you do not comply with the technical requirements for working with biomaterials, this can lead to an incorrect diagnosis.

Who should take a PCR blood test?

Anyone can take the study. The indication for it is suspicion of sexually transmitted infections (HIV infection, gardnerellosis, chlamydia). If unprotected sexual contact occurs accidentally, 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.

Pregnant women, as well as those who are just planning to conceive a child, must donate blood to the TORCH complex.

Although PCR is the most effective diagnostic method, you don’t need to focus on it. It is necessary to comprehensively examine the patient in the presence of any pathology. 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 human body’s response to the pathogen and medications. A PCR blood test for HIV must be prescribed by a doctor.

Features of the procedure and preparation

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

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

• prohibition on sexual intercourse one 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 into a sterile container.

One and a half or two days after the procedure, the PCR blood test will be deciphered and the result will be ready. There are even cases when you can get results 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 carry out proper preparation. It is a well-known fact that in laboratory research a large number of errors (up to about seventy percent) occur precisely during sample preparation.

Currently, some laboratories collect blood 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 personnel. Thanks to this, contamination of biological material can be avoided and the reliability of the analysis can be ensured as much as possible.

Decoding the results

The result of a PCR blood test can be positive or negative. If the blood test is negative, this indicates the absence of infectious pathogens in the material donated by the patient. A positive test 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 may be positive even in the absence of any symptoms of the disease. This indicates either the beginning of a pathological process, or that the person is a carrier. If the latter is detected, no treatment procedures are required. In this case, the patient is recommended to be constantly monitored by a doctor, which means, for example, periodic testing of PCR blood tests for herpes and other infections.

Most often they are found in the urethra, in scrapings made from the cervical canal, and in saliva. However, we must remember that a sick person can infect completely healthy people, even if he is not bothered by the disease in any way. It can become chronic. It must be said that if a positive result is obtained using PCR, it is necessary to prescribe appropriate treatment procedures.

Quantitative PCR characterization

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

Studying the results obtained will help the specialist choose the appropriate drug and specify the required dosage.

Diagnostic accuracy

There are three most important characteristics of PCR, namely:

Sensitivity;

Specificity;

Accuracy.

Diagnosis of infections using PCR has a high probability of detecting infectious agents in the body. The analysis of blood and other fluids is highly specific. Thanks to it, you can easily determine a specific infectious process by taking, for example, a PCR blood test for hepatitis or HIV. PCR diagnostics are also highly sensitive. If the test material contains a minimum amount of infectious agents, the PCR method will always be positive.

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

Detection 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 hidden nature:

• 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 consult a specialist. The results of a timely PCR blood test for chlamydia, borreliosis and other infections will help the doctor prescribe effective treatment.

STIs have a negative impact on the reproductive system. They can cause infertility or defects in the fetus. This is why it is important to take a PCR test before planning a pregnancy.

In the diagnosis of infectious diseases, various laboratory methods for detecting pathogens are used. One of the most progressive, specific and accurate laboratory tests is PCR analysis, which makes it possible to determine the presence of pathogens in the blood and other types of biological material, to detect microorganisms in the first stages of disease development, in cases of infection.

PCR analysis using special equipment

How are diagnostic tests performed using PCR?

Polymerase chain reaction is a laboratory molecular biological method for detecting DNA of bacteria and fungi, DNA and RNA of viruses. The basis of PCR is a special enzymatic reaction that occurs in the presence of special enzymes and substances of a molecular nature. Due to the fact that the method is able to detect the presence of the pathogen itself, it is considered the most informative and sensitive in identifying latent infections and carriage compared to all other diagnostic methods.

Analysis of biological samples using PCR testing allows you to quickly detect the presence of bacteria and viruses themselves.

Other laboratory diagnostic methods, as a rule, determine indirect signs of infection or require a lengthy testing procedure.

The main stages of the PCR method are:

• collection of biological material, its delivery to the diagnostic laboratory,
• isolating the genetic material of bacteria and viruses from the taken material,
• direct PCR analysis and decoding of the obtained data.

To perform a PCR reaction, samples of liquids, tissues, and secretions are used, in which the presence of pathogenic microorganisms is suspected. The most common samples used for testing are venous blood, plasma, or serum. In the laboratory, bacterial and viral particles are separated from other components and DNA or RNA molecules are isolated from them using special reagents.

Polymerase chain reaction

At the next stage, these genetic molecules are multiplied many times in special devices. To do this, special enzymes and molecules are used that make it possible to artificially propagate a strictly defined type of DNA belonging to only one specific pathogen. As a result of the reaction, a huge number of short DNA fragments are formed, identical to those that are part of viruses and bacteria.

In the third stage, the accumulated fragments are detected using special dyes and detection equipment. If the original sample contained pathogens, the reaction produces a specific product and the test shows a positive result. If there was no pathogen in the material, the reaction product is not synthesized and the test gives a negative result.

PCR testing is one of the fastest ways to diagnose infections. The full cycle of material testing takes from several hours to one day.

PCR method - the essence

It is the use of multiple reproduction of DNA molecules of a strictly defined type in the reaction that makes it possible to accurately determine the presence of microorganisms in biological samples with extreme sensitivity. Even a small concentration of infectious agents in the tissues and fluids of the body can lead to the synthesis of a huge amount of reaction product and a positive conclusion.

What infections are determined by PCR test?

Using PCR technology, the presence of a wide variety of bacteria, yeast-like cells, and viral particles is detected. In modern diagnostic practice, PCR analysis is most common for identifying pathogens of the following diseases:

• HIV infection (AIDS),
• hepatitis (hepatitis B, hepatitis C and other rarer varieties),
• cytomegalovirus infection,
• almost all infectious diseases of the genitourinary tract,
• candidiasis,
• mycoplasmosis,
• infections caused by herpes viruses,
• papillomavirus infection,
• toxoplasmosis,
• intestinal diseases,
• diphtheria,
• tuberculosis,
• rare focal infections,
• mononucleosis and many others.

Polymerase chain reaction is the most common, reliable and fastest method for detecting sexually transmitted infections, hepatitis, HIV, papillomas and other diseases.

For many diagnosed diseases, PCR is not the only diagnostic method. The diagnosis is confirmed by a doctor only when other signs of the disease are observed.

Scheme for identifying viruses and bacteria

But for a number of cases, the polymerase reaction is the “gold standard” for laboratory diagnostics.

The list of infections detected by PCR is expanding every year. The development of the method has already made it possible to simultaneously determine several pathogens. This contributed to the spread of comprehensive screening programs. Among them: a comprehensive study of microflora for bacterial vaginosis, determination of TORCH infections, identification of human papillomas of high and low carcinogenic risk. In addition, a PCR blood test is included in the mandatory hospital diagnostic complex.

Using the polymerase reaction, scientists were able to identify molecules that signal the development of various forms of malignant tumors - tumor markers. Thanks to this, the method has found application in the early detection of cancer. PCR tests are actively used to detect hereditary genetic defects, including in prenatal diagnosis and during pregnancy planning.

Features of biological material for PCR analysis

The collection of a certain type of material for research is determined by the type of infection that they want to diagnose as a result of testing. The following samples are taken as test samples:

• venous blood,
• saliva,
• scrapings, for example from the cervical canal, from the inside of the cheek,
• mucus samples,
• urine,
• pleural fluid,
• samples of semen and prostate secretions,
• sputum and bronchopulmonary lavage,
• discharge from the urethra.

The results can only be deciphered by specialists

In case of certain infections and for special indications, doctors may order a cerebrospinal fluid test. Samples of the placenta and amniotic fluid are used to detect intrauterine diseases.

In general, for diagnosis using PCR, they use the type of material in which the causative agent of the disease itself is most likely present. The type of biological material is determined by the doctor when sending it for analysis.

In order for the analysis to be accurate and correct, simple preparation is necessary before collecting the material and observing special cleanliness in taking samples and conducting the analysis itself.

To obtain an accurate analysis result, you should adhere to several rules for preparing and collecting material for research:

• abolish sexual intercourse a few days before collecting material from the genital organs and in the case of diagnosing sexually transmitted infections using a blood test,
• take venous blood for PCR analysis in the morning, do not drink or eat food before taking the test,
• do not smoke at least two hours before donating blood,
• Collect urine strictly in a sterile container immediately after sleep.

Important! Taking antibiotics and other medications may distort test results. Before submitting the material, you should consult your doctor.

If you plan to collect material from the genital organs to perform a PCR analysis, it is recommended to discontinue the use of antibacterial hygiene products and potent medications in consultation with your doctor.

How to decipher the result of a PCR analysis

The results of PCR analysis are usually presented in a qualitative format. The infectious agent is either detected in a sample of biological material or is not detected in it.

The interpretation of the conclusion in this case is as simple as possible:

• a positive result indicates that the microorganism was present in the analyzed sample,
• a negative test indicates that no infectious agent was detected.

Attention! A negative result is sometimes a consequence of improper sampling of material or errors during the analysis process.

If there are obvious symptoms of the disease and a false negative result is suspected, it may be advisable to repeat the test.

PCR analysis requires great precision

In special cases, quantitative methods for determining the pathogen are used. The results of such analyzes are given in the form of the resulting concentration of DNA or RNA of the pathogen in terms of a certain volume of material. For example, in copies of DNA molecules per milliliter of blood plasma.

Quantitative and semi-quantitative PCR analysis and interpretation of its results are performed to monitor the course of the disease, determine the viral load, identify the stage of the disease, and diagnose diseases caused by conditional pathogens.

Positive aspects of PCR diagnostics

The active implementation of the polymerase chain reaction method in the diagnosis of such a wide range of infectious diseases became possible due to a number of its advantages:

• high specificity of the method - the analysis allows you to detect a strictly defined type of DNA of pathogens,
• the ability to put analysis on stream and automate the process,
• high sensitivity of the method and the ability to diagnose the disease in the early stages,
• diagnosis of several infections simultaneously;
• speed of the procedure and low cost of consumables.

The disadvantages of the method include the need for expensive equipment, high requirements for cleanliness and manufacturability of the laboratory, and the possibility of obtaining false results if the analysis procedure is not followed.