How many days is a chlamydia PCR analysis done. About the polymerase chain reaction (PCR) for chlamydia. What is PCR analysis for chlamydia used for?

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As you know, every disease has its own, inherent only to it, signs. But it has nothing to do with chlamydia.
Chlamydia- this is a disease that does not have clear symptoms that are unique to it, and sometimes it is completely asymptomatic. And even if some are manifested, then most often they are similar to the signs of other STDs.
Therefore, laboratory research methods are decisive for making a diagnosis. Unlike many other diseases, the diagnosis of chlamydia is purely laboratory.

Who should be screened for chlamydia first?

  • Men and women who have many sexual partners, especially casual ones.
  • Persons whose sexual partners are found to have chlamydia, even in the absence of complaints and symptoms. After all, complications of chlamydia can develop even with its asymptomatic course. The risk of infecting a partner is about 90%.
  • Women suffering from infertility for more than 2 years, even if the sexual partner is examined and healthy.
  • Women with cervical erosion, cervicitis, inflammation of the ovaries (especially when planning pregnancy). Moreover, the vaginal smear may be normal.
  • Women with a violation of the course of pregnancy: spontaneous miscarriage, premature birth, polyhydramnios, fever of unknown origin during this pregnancy.

What are they researching?
To detect chlamydia, it is necessary to make a sampling of the material. It can be a scraping containing cells of a diseased organ - the vagina, cervix, prostate secretion, scraping from the urethra, conjunctiva of the eye. Such material can also be blood, urine and semen in men.

What tests are prescribed for chlamydia and how useful can they be?
First, we will dwell on the possible methods of examination, and then we will conclude which of them are most preferable.

2. Immunocytological analysis - Direct immunofluorescence reaction (RIF or PIF).
This method involves the direct detection of chlamydia antigens. For this, the material obtained by scraping is treated with special antibodies that are directly treated with a fluorescent substance. These antibodies bind to specific chlamydia antigens. Then, with fluorescent microscopy, chlamydial inclusions in the cells are determined by a green or yellow-green glow.
The immunocytological method is used in both the acute and chronic phases of the disease.
A significant disadvantage of RIF is a large number of false negative and false positive results. False-negative results are most often associated with violation of the rules for sampling biological material. False-positive results may be due to combined infections of the urogenital tract, when other microbial flora is present along with chlamydia. Among other things, the RIF is very subjective, because. depends on the experience and personal assessment of the laboratory assistant. Therefore, RIF gives a very high percentage of false positive results and cannot be considered reliable. The disadvantage of RIF is also that it cannot be used to evaluate the results of treatment.
With urogenital chlamydia, the accuracy of the method is about 50%.

3. Enzyme immunoassay (ELISA).
ELISA is a method for indirect detection of bacteria, i.e. the pathogen is not detected directly, but specific antibodies (IgG, IgA, IgM) to it are determined. The method is based on the ability of the immune system to produce antibodies ( immunoglobulins, Ig) in response to the introduction of foreign agents.
The advantages of ELISA are that it allows not only to identify the causative agent of the disease, but also to determine at what stage it is (acute or chronic) and evaluate the effectiveness of the treatment. The advantage is also the automation of the method and the speed of its implementation.

How are the results evaluated?
When infected with chlamydia, specific antibodies appear on the 5-20th day of the disease. In this case, the appearance of each class of antibodies occurs at a certain stage of the disease.

  • In primary infection, IgM appears first, then IgA, and lastly IgG.
  • The very first after the primary infection (after 5 days) appear IgM, which protect the body from the possible spread of infection. They are markers of the acute stage of the disease. By the 10th day, the amount of IgM in the blood reaches a peak. Then their level begins to decrease, and IgA appear. For a short period of time, IgM and IgA antibodies can be detected in parallel. This period indicates the height of the infectious process.
  • IgA can be detected 10 days after the onset of the primary symptoms of the disease. They protect the mucous membranes from the penetration of bacteria deep into the tissues. A high level of IgA in mucosal secretions indicates a well-functioning local immunity.
  • Then, 15-20 days after the introduction of Chlamydia trachomatis into the body, IgG appears in the blood, and the level of IgA decreases.
  • The acute primary process is characterized by a high level (titer) of IgM in combination with a low titer of IgG.
  • With re-infection, there is a rapid increase in the titer of IgG and IgA and the almost complete absence of IgM.
  • In the chronic course, specific IgG and A are detected, the concentrations of which do not change for a long time.
  • When cured after 1.5-2 months, IgA and IgM are not detected in the blood, and IgG can persist for several years, but their level decreases by 4-6 times.
  • Long-term detectable IgG indicates past chlamydial infection.
  • With an exacerbation of chlamydia, the amount of IgA and IgG increases several times.
  • The effectiveness of the treatment is determined by the presence of IgA. If IgA is detected in the blood 2 months after the course of treatment, this means that the infection has remained.

It should be noted that specific antibodies produced to chlamydia do not provide stable immunity against them.
The accuracy of this test for chlamydia is about 70%. This is due to the fact that antibodies to chlamydia can also be present in healthy people due to a previous illness, as well as be determined in respiratory and other types of chlamydial infections.

4. Polymerase chain reaction (PCR).
Using PCR, a specific site or DNA fragment of chlamydia is detected in the material under study, therefore, in comparison with other methods, it is impossible to confuse chlamydia with some other infection. It is effective in both acute and chronic phases of the disease. At the same time, very little material is needed for analysis, but the results are ready in 1-2 days.
For PCR research, the material can be scraping from the urethra or cervical canal, prostate secretion, urine sediment, scraping from the conjunctiva of the eyes, blood.
When diagnosing a primary infection, it is more informative to identify this infection in the places of initial localization, i.e. the material should be scrapings from the genital tract. False-positive PCR results may be in case of violation of the process of sampling, transporting the material and conducting the analysis itself.

Important! To assess the effectiveness of PCR treatment, the study cannot be carried out earlier than a month after the course of antibiotic therapy, because. you can get false positive results. This is due to the fact that when a DNA fragment of chlamydia is detected, it is impossible to assess how viable the microbial cell itself is. In this case, the viability of chlamydia, as well as the possibility of recurrence of the disease associated with it, is assessed using a microbiological method. If chlamydia is not viable, then despite the presence of a DNA fragment, microbial cells will not grow in cell culture.
To date, the accuracy of this method is the highest - up to 100%.
This method is recommended as the preferred method in the diagnosis of chlamydial infection.

5. Microbiological examination (cultural method) with the determination of sensitivity to antibiotics.
The essence of this method is that the studied material is sown on a special medium and grown. Then, the pathogen is identified by the nature of growth and other signs. The cultural method is the most sensitive, it allows not only to identify viable chlamydia, but also to select an antibiotic to which this microorganism is sensitive.
Scraping from the urethra, cervix, prostate secretion, scraping from the conjunctiva of the eye can serve as material for research.
One month before the study, antibiotics should not be used.
Microbiological examination is preferable to carry out in the following cases:

  • To evaluate the effectiveness of the antibiotic treatment.
  • To detect sensitivity to antibacterial drugs.
  • To detect chlamydia in people with immunodeficiencies (HIV infected, cancer patients after radiation and chemotherapy, people receiving immunosuppressants, etc.).

The disadvantages of the cultural method for diagnosing chlamydia are the complexity, high cost and duration of the study. It also requires special laboratory equipment and very high qualification of personnel. In addition, this method, like no other, requires impeccable compliance with the rules for the collection of material, transportation and storage.
The actual term for obtaining results by this method is at least seven days.
The detection rate of chlamydia during sowing is up to 90%.

6. Express diagnostics.
All methods of rapid diagnosis of chlamydia are based on enzyme-specific reaction and immunochromatography. For this, special kits for express diagnostics are used, which allow you to visually evaluate the results in 10-15 minutes. This is a very fast and convenient method, but its accuracy is only 20-25%.

Conclusions.

  • There is no single method that would detect chlamydia in 100% of cases. Therefore, in most cases, laboratory diagnostics should include a combination of at least two methods.
  • The most sensitive tests for chlamydia are PCR (DNA - diagnostics) and microbiological analysis. They are the "legal standard" for diagnosing chlamydia.
  • In the case of primary infection, one PCR test is usually sufficient before the use of antibiotics.
  • In chronic processes - PCR or microbiological test, or RIF + ELISA.
  • With the probability of the transition of the pathogen into the L-form - ELISA.
  • Microbiological examination is ideally used to evaluate the effectiveness of treatment. If it is impossible to conduct it - PCR + ELISA.
  • To determine the stage of the disease - ELISA.
  • In patients with immunodeficiencies, ELISA is not informative; ideally, a microbiological method should be used.
  • You should not rely too much on the results of determining the sensitivity of chlamydia to antibiotics. After all, as you know, microorganisms behave differently in a test tube (in vitro) and in a living organism (in vivo).

Content

A serious infection, often sexually transmitted, is dangerous with severe consequences. Laboratory diagnostic methods - blood tests for chlamydia - help to identify the disease, start its treatment. What are the features of surveys, how informative are all their varieties, how the results are deciphered - questions that are interesting to get answers to.

Chlamydia trachomatis - what is it

  • during unprotected intercourse;
  • household way;
  • during pregnancy from an infected mother to a child;
  • for men, the disease is dangerous by the development of prostatitis, impotence, chlamydial pneumonia;
  • in women, chlamydia provoke miscarriages, adhesions in the pelvis, premature birth, tumors of the uterus.

Diagnosis of chlamydia

The disease may be asymptomatic for a long period after infection. Often chlamydia is detected in the diagnosis of other sexually transmitted infections. Due to the characteristics of the biological cycle of the pathogen, analyzes are carried out in several ways. Laboratory diagnosis of chlamydia includes research methods:

  • primary microscopic analysis of the smear;
  • cultural method - sowing biomaterial in a special environment - gives an accurate result;
  • RIF of chlamydia - determination of the immunofluorescence reaction - pathogens glow under a microscope, it is reliable.

Analysis for chlamydia

Blood tests are the most accurate diagnosis for detecting chlamydial infection. They are produced according to several methods that have their own characteristics. The main types of examination:

  • Immunoassay - ELISA. By the amount of Igg, Igm, Iga antibodies, it is determined which phase is currently observed in the disease - acute, chronic or remission.
  • Polymer chain reaction - PCR. Detects pathogen DNA, is a very reliable diagnostic method.
  • having unprotected sex with a new sexual partner;
  • women who have frequent ailments due to pelvic diseases;
  • both partners when planning pregnancy, so as not to infect the expected baby;
  • women who have problems bearing a child;
  • patients with unexplained causes of infertility.

Blood for chlamydia is taken from a vein. To obtain objective results, doctors recommend that you comply with the requirements:

  • do tests not earlier than a month after antibiotic treatment;
  • do not have sexual intercourse in the coming days before the examination;
  • do not smoke half an hour before blood sampling;
  • come to the study on an empty stomach;
  • do not drink alcohol during the day;
  • do not drink water before testing;
  • exclude the implementation of physiotherapy.

PCR for chlamydia

With this research method, chlamydia in the blood is determined by the amount of DNA of microorganisms that are in the selected sample. Polymer chain reaction analysis - PCR - is characterized by very high accuracy and sensitivity. The result is fast and reliable. It is considered positive with a large number of chlamydia in the sample for research - the cause of infection is confirmed. The advantage of the method is that it detects infections:

  • in a hidden form;
  • oligosymptomatic;
  • at the acute stage.

Chlamydia poses a great danger to a woman who is expecting the birth of a baby. There is a high probability of intrauterine infection. Timely diagnosis will help to start treatment at an early stage, to avoid serious problems. Chlamydia PCR analysis is prescribed by gynecologists to exclude infection when a pregnant woman has symptoms:

  • elevated temperature;
  • soreness in the lower abdomen;
  • bad feeling.

The PCR blood test is universal. With its help, not only the causative agent of chlamydia is determined, but also other infections - herpes, tuberculosis, hepatitis. When decrypting, two options are possible:

  • negative - indicates the absence of infection of the body;
  • positive - indicates that infection has occurred, and by what type of bacteria.

ELISA for chlamydia

From the first days of infection, the body begins to produce antibodies to chlamydia in the blood. Three types of immunoglobulins stand up to protect against the disease, which are called Igg, Igm, Iga. Enzyme-linked immunosorbent assay - ELISA for chlamydia not only accurately determines their presence, but states the stage in which the disease is located. This is due to the appearance of each of the antibodies at a particular stage of infection.

When examining blood by ELISA, immunoglobulins are detected at the following times:

  • after infection, Igm immediately appears, if the other two are absent, acute inflammation is diagnosed, it is important when examining newborns;
  • a month after infection, Iga antibodies are formed, which indicate the progression of the disease;
  • the appearance of Igg signals the transition of chlamydial infection into its chronic form.

Deciphering the analysis for chlamydia

Interpretation of the results of the survey has subtleties, so it should be carried out by qualified specialists. A blood test for chlamydia ELISA stands for each type of immunoglobulin, indicates the period of development of the infection. When determining Igm, the results are:

  • Positive: less than two weeks have passed since infection; if other antibodies are not detected, in the presence of Igg, an exacerbation of chronic inflammation.
  • Negative: no chlamydia - in the absence of all immunoglobulins; when Igg is detected - infection occurred at least two months ago.

In blood tests for the presence of Iga antibodies, the result is interpreted as follows:

  • Positive: acute stage of chronic infection or infection more than two weeks old; infection of the child during pregnancy.
  • Negative: no chlamydial inflammation; from the time of illness less than 14 days; there is little chance of fetal infection.

When decoding the test for Igg, the following results are produced:

  • At the norm - absent, the value of the coefficient of positivity is in the range of 0–0.99;
  • Positive: Chlamydia infection or flare-up occurred more than three weeks ago.
  • Negative - in case of simultaneous absence of Iga Igm immunoglobulins: no chlamydia in the blood; full recovery.

Where to get tested for chlamydia

Those who have felt signs of the disease, had unprotected sex with a casual partner, can be purchased at the pharmacy for an express test. With its help, the presence of chlamydia infection is quickly determined. For analysis, you need urine or a smear in women. The instructions describe how to collect them. The result is decoded like this:

  • positive - requires immediate contact with a venereologist for the appointment of drug treatment;
  • a negative test indicates that the disease is absent at the time of the test.

You can get tested for chlamydia by referral from a venereologist or gynecologist. It is not excluded that the patient independently applies to medical institutions if infection is suspected. A blood test for chlamydia is carried out by such organizations:

  • women's consultations;
  • family planning clinics;
  • skin and venereal dispensaries;
  • specialized laboratories for research.

How much does a chlamydia test cost?

Testing for chlamydia can be done at clinics or specialized centers that provide such services. The cost depends on the status of the institution, the available equipment. The classification of specialists involved in deciphering the results plays a role. The price of analysis for chlamydia in medical organizations in Moscow is summarized in the table:

Video: how to take a blood test for chlamydia

Attention! The information provided in the article is for informational purposes only. The materials of the article do not call for self-treatment. Only a qualified doctor can make a diagnosis and give recommendations for treatment, based on the individual characteristics of a particular patient.

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Description

Method of determination PCR with real-time detection.

Material under study Urine

Determination of Chlamydia trachomatis DNA in urine by polymerase chain reaction (PCR) with real-time detection.

Features of the life cycle of Chlamydia trachomatis lead to the frequent occurrence of a persistent form of infection, resistance to therapy. Reactivation of the infection can occur under the influence of changes in the immune or hormonal status, trauma, surgery, stress. Chlamydia trachomatis has low immunogenicity, as a result of which antibodies are not detected in 50% of infected people. Therefore (especially in doubtful cases, in the absence of seroconversion), the microorganism is detected by a highly sensitive and specific direct method - PCR.

Analytical indicators: for the detection of C. trachomatis DNA in clinical samples by polymerase chain reaction (PCR):

  • the fragment being determined is a specific DNA region of Chlamydia trachomatis;
  • detection specificity - 100%;
  • the sensitivity of the analysis is 100 copies of Chlamydia trachomatis DNA in the sample.

Preparation

The first morning portion of urine in the amount of 20-30 ml should be collected in a sterile vial. It is not recommended to take biomaterial against the background of antibiotic therapy.

Indications for appointment

  • acute phase of the disease.
  • Establishment of the etiology of a chronic infectious process of the urogenital tract, including its upper sections, the ability to detect single DNA molecules of chlamydia cells that are not detected by other methods.
  • Pregnancy with burdened obstetric history.
  • Infertility.
  • Monitoring the effectiveness of therapy (not earlier than one month after the end of taking antibacterial drugs).
  • Preventive screening studies (to exclude the possibility of an asymptomatic infection).

Interpretation of results

The interpretation of test results contains information for the attending physician and is not a diagnosis. The information in this section should not be used for self-diagnosis or self-treatment. An accurate diagnosis is made by the doctor, using both the results of this examination and the necessary information from other sources: history, results of other examinations, etc.

Quality test. The result is returned in terms of "found" or "not found".

  • “detected”: a DNA fragment specific for Chlamydia trachomatis was found in the analyzed sample of biological material; Chlamydia trachomatis infection;
  • “not detected”: no DNA fragments specific for Chlamydia trachomatis were found in the analyzed sample of biological material or the concentration of the pathogen in the sample is below the test sensitivity limit.

Please note that the timing of PCR studies may be extended when confirmatory tests are carried out.

Chlamydial infection is a sexually transmitted disease. The insidiousness of this "infection" is that it does not manifest itself in any way with obvious symptoms and is difficult to identify. But untreated, chlamydia causes secondary female diseases and leads to miscarriage.

A normal smear from the vagina or urethra is not able to detect the causative agent of chlamydia. Chlamydia live and multiply inside other cells, so they are inaccessible to most routine tests.

How is a PCR test done for chlamydia?

For the diagnosis of chlamydia, a whole range of laboratory tests is used, the most important of which is PCR analysis. The polymerase chain reaction method with high accuracy detects the presence of chlamydia in the body based on the study of DNA cells of biological material.

The PCR method reveals not only actively multiplying in the acute stage of the disease, but also latent chronic chlamydia.

How is a PCR smear taken for chlamydia?

The patient's venous blood is often taken for research, but most often in antenatal clinics they practice taking discharge from the genital tract. The analysis is taken no earlier than 3 days after the end of menstruation. Material for analysis is taken in the form of a smear from the vagina, urethra, cervix. After a scraping, a woman may experience pain when urinating, and small spotting is acceptable.

A swab for chlamydia by PCR should be regularly taken by people who lead a promiscuous intimate life. The analysis is also carried out in case of detection of a disease in a sexual partner or the appearance of unpleasant symptoms. Examination of pregnant women is mandatory.

Characteristics of the PCR method

This is the most informative research method, on the basis of which the final diagnosis is usually made. Other methods require additional confirmation. PCR analysis is an accurate method, it is prescribed by most doctors, and it is convenient for the patient.

The polymerase chain reaction is the latest development in molecular medicine. This study is based on a series of actions during which the infectious agent is detected and identified. Despite the complexity in execution and the detailed study of the material, the result can be obtained in a few days. You should not use express diagnostics, it does not always make it possible to detect chlamydia.

You need to know how this analysis is taken. The test will require blood, urine, or urethral discharge. Preparation for the fence has its own characteristics. It is recommended to take blood for chlamydia on an empty stomach. You can not drink water and use chewing gum. Otherwise, the PCR analysis may give an incorrect result. Men are tested for:

  • smear from the urethra;
  • seminal fluid.

Patients must abstain from intimacy 24 hours before delivery and pre-ejaculation. It negatively affects the results of the study. There are other rules that must be followed.

Urine for PCR analysis can be collected both at home and in the laboratory. In the first case, it is necessary to urinate into a sterile container immediately after waking up. For detection, the first portion of urine is used. The received material must be delivered to a medical facility within 3 hours. A positive result of the analysis is an indication for additional testing. An integrated approach allows you to determine the form and severity of the disease.

How is the procedure performed

The procedure for passing the analysis for men and women is different. Most of all, this concerns the process of collecting secretions from the genital organs. In women, the swab is taken from the vagina or urethra. In order for the study to give the correct result, it is recommended:

Donate blood. This type of study does not harm the developing child and allows you to get a complete picture of the disease. The same method is used for chronic chlamydia. It is more difficult to determine the infection in the urine.

PCR analysis in men involves taking a smear from the urethra or seminal fluid. Preparation is not much different from that of women:

  1. You should refrain from urinating for 3 hours before donating the material. This will ensure the reliability of the result of the study of the urethral smear.
  2. If it is necessary to take seminal fluid, the last sexual intercourse should take place no later than one day before visiting the laboratory.
  3. Do not use pills and gels to stimulate an erection. Such drugs negatively affect the hormonal background of a man's body, because of which the purity of the seed is violated and the result of the analysis may be incorrect.

Decryption Features

Processing the material takes no more than half an hour. In the course of the study, DNA fragments are repeatedly copied. The nucleotide chain is formed under the influence of the enzyme - polymerase. To start a reaction, a substance needs a launch pad, which is catalyzed by synthetic oligonucleotides. The polymerase sequentially adds nucleotides to form DNA templates. Thus, 2 new fragments are produced in one temperature cycle. In 25–35 cycles, billions of copies of a piece of DNA accumulate in a test tube.

Deciphering the results takes about 8 hours. However, to increase the reliability, many experts recommend to donate blood in parallel for the presence of antibodies to chlamydia. This will help determine the stage and nature of the course of the disease and select the most effective therapeutic regimen. The norm is the result when chlamydia trachomatis is absent in the obtained sample. Material for PCR analysis must be taken by both partners, otherwise the treatment will be useless.

Disadvantages and advantages of the method

One of the main advantages of PCR diagnostics is high accuracy. The positive characteristics include the fact that on the basis of its results it is possible not only to detect the presence of chlamydia in the body, but also to detect other STIs. To perform the study, minimal amounts of material are required; a blood test for chlamydia can be performed in each laboratory.

The disadvantage is the frequent receipt of a false positive result. This is due to many factors, the elimination of the influence of which is not always possible. Therefore, if chlamydia is detected in a smear, serological tests should be used. A negative result also does not always indicate the absence of an infectious agent.

The final diagnosis is based on the results of laboratory tests, examination of the patient and the clinical picture of the disease.

Chlamydia belongs to the category of infections that are discovered by chance. This is due to the asymptomatic course, in which the disease still affects the internal organs. In order to avoid the development of dangerous complications, it is necessary to undergo an annual examination. An indication for PCR is the presence of indirect signs of the disease, because timely detection and treatment of chlamydia leads to complete recovery.