PCR analysis for infections. PCR: a method that is too good Leading laboratory specialist what PCR do

Most people are tested for infections using the PCR method at least once in their lives. But few people know what it is and what the essence of the study is.

Diagnosis of infections using PCR is based on the detection of DNA or RNA of a pathogenic microorganism. It can be detected in any clinical material obtained by invasive or non-invasive methods. It reveals the genetic material of the pathogen, which is copied many times. A specific fragment of genetic code corresponding to the standard is determined.

If it is present in clinical material, the result will be positive.

Advantages of PCR diagnostics of sexually transmitted infections:

• high accuracy and information content;
• minimal risk of false positive or false negative results;
• using PCR, infections can be diagnosed in any clinical material;
• almost any pathogen can be detected;
• The study is carried out quickly - results can be obtained within a few hours after the test.

Currently, PCR diagnostics of infections is one of the main methods for detecting most sexually transmitted diseases.

PCR analysis of infection with quantitative assessment

Most often, doctors prescribe high-quality PCR tests for infections. That is, the result can be either positive or negative. But in some cases quantitative research is required.

It differs in that, in addition to the fact of the presence of the pathogen in the structures genitourinary system, its concentration in clinical material is determined.

Quantitative PCR for infections is necessary in the following cases:

• when diagnosing infections that are considered opportunistic (in which case they can cause inflammatory processes only when the bacterial population increases excessively);
• to assess flow dynamics pathological process and effectiveness of therapy;
• to assess the prognosis of the disease, determine the risk of complications, and select adequate therapy.

Is it painful to take a smear test for PCR infection?

Most tests are painless or cause minimal discomfort to the patient. PCR alone cannot cause pain, because it is carried out in a laboratory, away from the patient.

Only the procedure for collecting clinical material can be unpleasant. And it can be different. Obviously, if urine or ejaculate is taken for analysis, the analysis will not be painful. At the same time, if the cerebrospinal fluid, scraping from the urethra, secretion prostate gland, then the collection of biomaterial will be unpleasant to one degree or another. Most often, a scraping of urethral cells is taken to diagnose sexually transmitted infections. This procedure is usually unpleasant, but in our clinic it is performed painlessly.

What are the differences between a smear and a blood test for PCR infection?

As already mentioned, different clinical material. A smear from the urethra identifies those pathogens that are present in the structures urethra. But they are not always there. Therefore, it is often necessary to examine other biomaterial, for example, blood.

Here are the infections you can test for with a smear:

• PCR analysis of bacterial infections - gonorrhea, chlamydia, ureaplasmosis, mycoplasmosis;
• trichomoniasis;
• viruses – HPV, herpes;
• fungi - candida.

Here are the infections you can test for in your blood:

• PCR analysis of viral infections - HIV, viral hepatitis, herpes, cytomegalovirus;
• bacterial pathologies – syphilis (rare);
• any sexually transmitted pathologies in case of their generalization (gonorrhea, candidiasis).

In practice, blood PCR is most often carried out when there is a suspicion of viral infections, which may not stand out in external environment through the urethra.

Who needs diagnosis of infection using PCR?

Main indications for PCR analysis for infections:

• control after treatment;
• presence of symptoms of a sexually transmitted disease;
• history of unprotected sexual intercourse with a new partner;
• detection of infections in a regular partner;
• examination before pregnancy, IVF, surgery;
• Diagnosis of infertility in order to determine its causes.

Some people are examined without indication, for preventive purposes.

This is due to the fact that most sexually transmitted infections can occur without symptoms. However, they still spread throughout the population, cause complications and pose a danger to reproductive health. Therefore, every person who is active sex life, changing partners from time to time, should be examined for infections at certain intervals. It is advisable to be examined once a year. A standard PCR test for 12 infections will take a maximum of half an hour of your time. But it will allow timely detection of dangerous diseases.

PCR analysis of infection - how to prepare for smear and blood

Before taking a smear, you must not have sex for 2 days and not urinate for 2 hours.

There is no need to prepare for a blood test. Regardless of what clinical material you submit, you should not take antibiotics until the diagnosis is completed.

How to evaluate the result of a PCR test for infections

When carrying out PCR diagnostics of infections, interpretation of the results is carried out only by a doctor. At first glance, it does not present any difficulties.

After all, the analysis form most often gives a positive or negative result. But it is important to take into account the symptoms, data from other tests, and medical history data. Sometimes PCR test results for infections are false positive. In other cases, the results of PCR analysis for infections are false negative.

In the first case, an infection is detected that actually does not exist. In the second case, the pathogen present in the body is not detected. For the result to be reliable, it is important to understand when positive test PCR for infections after infection. It is advisable to carry out diagnosis no earlier than 2 weeks after unprotected sex.

PCR analysis for infections - which doctor prescribes

Diagnosis of infections using PCR is used in many branches of medicine. One of the main areas of application is venereology. Such tests are prescribed by a venereologist, less often by a gynecologist or urologist.

If you are looking for where to get a PCR test for infections, come to our clinic.

Our advantages:

• painless collection of clinical material;
• rapid diagnostic tests;
• no queues
• high diagnostic accuracy;
• the opportunity to consult a doctor and, if necessary, prescribe treatment.

The production time for a PCR infection test usually does not exceed 1 day. In some cases, it is possible to get results within a few hours. But the price of urgent diagnosis is higher. Our clinic conducts research on certain diseases, as well as complex analyzes PCR for 12 infections.

The price of diagnostic procedures depends on a number of factors:

• urgency of diagnosis;
• clinical material used;
• number of pathogens.

Our clinic works with several laboratories. This allows us to provide wide range diagnostic services and low research prices.

If you need to take PCR tests for infections, contact competent venereologists.

PCR analysis - highly accurate diagnostic test, allowing to detect pathogens infectious diseases according to their genetic material (RNA, DNA) in a sample of biological fluid taken from a person.

Polymerase chain reaction makes it possible to diagnose a wide range of diseases of viral etiology, including those present in the human body long time, occurring latently. Most often, PCR analysis is prescribed in gynecological and urological practice.

Main indications

PCR analysis is prescribed if the following pathologies are suspected:

• viral hepatitis (A, B, C);
• cytomegalovirus infection;
• gastrointestinal infections (enteroviruses);
• herpes zoster (shingles);
• Filatov's disease (monocytic tonsillitis);
• neurollosis (granulomatosis of newborns).

The ability to use not only venous blood as a biomaterial significantly expands the list of pathologies diagnosed by PCR. This list includes:

• bacterial vaginosis;
• salmonellosis;
• diphtheria;
• various forms of tuberculosis;
• human papillomavirus;
• STI;
• mycoplasma hominis;
• Ureaplasma urealiticum.

How to prepare for research

Preparation for diagnosis using the PCR method depends on what type of biological material will be investigated. When donating blood 3 days before, alcohol intake and blood thinning medications are excluded, and adherence to a certain diet is recommended. When taking a smear from the urethra and vagina 3-5 days in advance, it is excluded intimacy, douching should also not be done at this time. Smears are not taken during menstruation, before it and for 5 days after it ends.

Features of the analysis

Biological material for PCR research can be blood, saliva, or smears. The choice depends on the type of virus or infectious pathology. If sexually transmitted diseases are suspected, morning urine and scrapings from the vaginal mucosa are collected. For herpes, hepatitis, HIV - deoxygenated blood, in a volume of at least 5 ml. In case of damage to the central nervous system, the biomaterial is spinal fluid.

PCR is used in the diagnosis of intrauterine pathologies of the fetus (the material is placental tissue), for pulmonary infections (fluid from pleural cavity or sputum).

There are several methods for performing PCR analysis:

• real-time diagnostics;
• determination of amino acid and nucleotide sequence of DNA;
• DNA sequencing method;
• nanofluidics.

Real-time research is most often used and is one of the most informative methods, gives maximum low percentage false positive results. The analysis is carried out within 24 hours.

The conclusion indicates one of the options for the study result - positive (confirms the presence of a pathological process) or negative (indicates its absence).

PCR(polymerase chain reaction) is an analysis method based on obtaining a reliable result from a minimum number of DNA fragments of the test material, confirming the identity of this nucleic acid a certain type living organism (bacteria, virus, protozoa, fungus).

The inventor of the PCR method in 1983 received Nobel Prize, for the most accurate and highly informative method of diagnosing infectious diseases, for the 100% reliability of the method.

Basis of the PCR method

During the research process, a DNA fragment is duplicated in an artificially created environment, outside the body. As a result of analysis, under the influence of specific enzymes, DNA molecules are increased to the amount necessary for identification using microscopic examination.

The program copies only those DNA molecules that are present in the analyzed material. This feature of the method allows not only to determine the types of infection, it is also used to establish paternity in genetic engineering.

The PCR method makes it possible to identify latent infections and infections whose pathogens have a long period growth, which makes them invisible during bacteriological culture.

Application of the PCR method

The PCR method is possible to determine any type of infectious agent. Many microorganisms acquire the L-form when exposed to antibacterial drugs and remain hidden for microscopy and immunological analysis.

PCR is especially widely used for the diagnosis of latent or indolent inflammatory diseases, if it is not possible to isolate the infection in any other way. First of all, this applies to the following sexually transmitted infections:

• hepatitis C and B,
• papillomavirus infection,
• gardnerellosis,
• herpes.

In therapeutic activities, PCR tests are used for diagnosis:

• pneumonia,
• pleurisy, difficult to treat,
• for isolating Helicobacter bacteria during chronic gastritis with a tendency to erosion,
• to identify a tendency to oncological diseases– detection of oncoviruses.

The material for PCR analysis is:

• blood,
• , cervix, vagina,
• glandular secretions, saliva, sputum,
• discharge from erosions and ulcers, others.

Where to undergo PCR testing

The PCR method is a complex sequential chain of many stages and cycles. Specific chemical compounds for media and enzymes are used to carry out the analysis. The analysis must be performed by a laboratory doctor who has undergone special training for laboratory research on high-precision equipment using computer technology.

The “Your Doctor” information desk has information about private clinics that have laboratory equipment and reagents in their arsenal that meet the requirement for analyzing material using the PCR method. All manipulations for collecting blood or other material are carried out in these institutions using sterile instruments and materials, in accordance with the requirements of the Ministry of Health of the Russian Federation to combat the spread of infectious diseases.

Many clinics of the Help Desk “Your Doctor” use vacuum systems for drawing blood, which completely eliminates the theoretically possible error in the examination result and greatly increases the objectivity of the analysis.

Publication date: 2019-06-12

This article is posted for educational purposes only and does not constitute scientific material or professional medical advice.