Toxoplasmosis: interpretation of tests. Diagnosis of toxoplasmosis

Not everyone knows that they are carriers of an infection such as toxoplasmosis. This disease rarely causes severe symptoms, so a person does not even suspect infection. But is it harmless toxoplasmosis? In the world, there have been cases of serious complications after infection with the disease. It is extremely dangerous to get infected during pregnancy. Therefore, in some cases it is important to undergo a timely examination for toxoplasmosis. The interpretation of the tests for this infection requires special medical knowledge. We will try to explain the essence of the main modern methods of diagnosing the disease, we will tell you what their advantages and disadvantages are, we will help to decipher the obtained results.

Toxoplasmosis - what is it?

In order to understand the essence of methods for diagnosing toxoplasmosis, it is important to understand what this ailment is. So, toxoplasmosis is an infectious disease, the causative agent of which is the Toxoplazma gondii parasite. The bearers of oocysts (spores of parasites) are cats. But other animals can become intermediate hosts. With excrements of mammals, toxoplasmosis spores are introduced into the soil. Therefore, you can get infected if you do not comply with hygiene standards during contact with animals, eating raw meat, unwashed vegetables and fruits. Infection occurs also in utero - from the infected mother to the fetus.

The disease is transferred once, after which the body produces persistent immunity in the form of antibodies, thereby protecting the person from re-infection with a disease such as toxoplasmosis. The analysis of the analyzes is carried out taking into account this peculiarity of the organism.

Than toxoplasmosis is dangerous?

In most cases, toxoplasmosis does not cause severe symptoms and complications in an adult with normal immune response. But in people with reduced protective forces of the body there may be irregularities in the work of the nervous system, fever, increased liver, eye damage.

Especially dangerous infection with toxoplasmosis is during pregnancy. Infection penetrates to the fetus and infects it. The medical prognosis in this case is unfavorable - miscarriage, premature birth, stillbirth are possible. In case of successful delivery, the child may have congenital disorders of the nervous system, serious damage to the internal organs, often incompatible with life. In connection with such a high level of danger for the normal course of pregnancy and development of the fetus during the conception planning period, as well as throughout the period of gestation, the woman is assigned laboratory tests to determine the acute phase of the disease, namely, the primary infection. Decoding of the analysis for toxoplasmosis in pregnancy should be done only by a specialist and taking into account all the factors influencing the study.

Methods of diagnosing infection

Methods for diagnosing toxoplasmosis can be divided into 3 large groups:

1. Serologicheskie based on the detection of biological material antibodies to infection, which are produced in the body immediately after infection. The advantage of such a survey is the ability to detect a quantitative indicator of antibodies, which helps determine the duration of infection, thereby highlighting the acute period of a disease such as toxoplasmosis. The interpretation of this type of assay is carried out by determining the quantitative detection of IgG and IgM immunoglobulin proteins. The disadvantage of this type of diagnosis is non-informativity for HIV-positive people, because in their body the immune system is weakened and only antibodies to infections are produced in small amounts.
2. Parasitic ones are based on the detection in the blood of parasites - causative agents of toxoplasmosis. A significant drawback of this type of diagnosis is the lack of the ability to determine the duration of infection, and accordingly, it is impossible to distinguish the acute phase of the disease. The interpretation of the analysis for toxoplasmosis in this case occurs when the parasite is directly detected in the material under study.
3. The hardware is used as an additional means of stating or refuting the diagnosis of toxoplasmosis in difficult cases from the point of view of diagnostic medicine.

More often than other methods the analysis of a blood on a toxoplasmosis is used. Deciphering the results is usually not difficult and is done serologically.

Serological methods of diagnosis

To determine the antibodies to toxoplasmosis, the following diagnostic methods are used:

1. RIF, or immunofluorescent reaction , is carried out in this way: with the help of special chemical reagents the material is diluted. In a special microscope that displays ultraviolet light, antibodies will be visible. If there is toxoplasmosis, the glow will be bright - this result is displayed in the form: +++ or ++++.
2. The RNG, or indirect hemagglutination reaction , is based on the erythrocyte property when precipitating certain chemical reactions. If, after carrying out the necessary laboratory manipulations, the red blood cells have covered the bottom of the tube - the result is positive. It is designated as follows: "intensive reaction +++" and "a strong reaction ++++".
3. ELISA, or the method of enzyme immunoassay , is used to determine toxoplasmosis more often than others, as it has a number of advantages: it is carried out quickly, with the help of special equipment, it has the ability to trace dynamics, and also to analyze 2 types of immunoglobulins IgG and IgM. To conduct such an analysis, test systems from the Czech Republic and Finland are used. Such tests can be successfully carried out by all groups of subjects, including HIV-infected people.

Decoding of the analysis for toxoplasmosis by ELISA

In order to properly decipher the results of the analysis for toxoplasmosis by the ELISA method, one must understand the essence of the biological processes of infection. Antibodies of protein groups of immunoglobulins of the IgG and IgM type are produced by the body to fight the pathogen and protect against secondary infection. IgM antibodies are produced by the body immediately after infection with toxoplasmosis, they remain in the body for up to a month, after which gradually the indices decrease and completely disappear. Thus, the detection of antibodies from the IgM group in the assay is a sign of an acute form of toxoplasmosis.

Immunoglobulins such as IgG begin to be produced in the body on the 3rd day of infection and protect the person against repeated infection with toxoplasmosis throughout their life. Thus, the detection of antibodies of this group and the absence of IgM indices indicate that the body is protected, therefore there is no cause for concern. But there are other variants of the results of the analysis for toxoplasmosis by ELISA. Then decoding the analysis for toxoplasmosis requires additional examinations to confirm the acute form of the disease or lack thereof. The variants indicated in the table are possible.

Analyzing the table, it can be noted that it is difficult to identify acute toxoplasmosis. IgG positive - interpretation of the analysis can speak of both previous infection and primary infection. But the presence of IgM antibodies usually indicates an acute stage of the disease.

Torch infection during pregnancy

In the period of pregnancy planning and early gestation of the fetus, doctors prescribe a comprehensive analysis, which has the abbreviation TORCH. Studies are carried out on infections that are transmitted in utero and cause serious developmental disorders of the fetus. Such diseases include toxoplasmosis, rubella, cytomegalovirus, herpes simplex, syphilis. The analysis is carried out by a serological method of research, namely ELISA. The analysis of the results of the analysis for torch infection is also carried out using the ELISA method described in the table.

Parasitic methods of diagnosis

Determine the presence or absence of parasites - causative agents of toxoplasmosis - with the help of microscopy of the material (blood, saliva, tissue samples with biopsy). This method is not very informative: it does not have the ability to track the process in dynamics and determine the duration of infection.

To date, this type of parasitic method of diagnosing toxoplasmosis, such as polymerase chain reaction, is used. With the help of this study, the DNA of the parasite is isolated. In this way it is possible to detect the pathogen even with a small quantitative ratio of it in the material. But the interpretation of the result of a blood test for toxoplasmosis using the PCR method does not make it possible to determine the prescription of infection and to track the dynamics of the disease. This method is prescribed by doctors as an additional study in the presence of controversial results of serological tests, in particular, the diagnosis of ELISA, as well as the impossibility of carrying out other methods for detecting toxoplasmosis in a specific clinical case. Often a PCR method is used to determine toxoplasmosis in children of the first year of life and AIDS patients, when the time factor is not a priority.

With the help of this method of diagnosis, the doctor can easily determine the diagnosis of "toxoplasmosis" - the analysis of the analyzes does not present any difficulties. So, a positive result indicates the presence of a parasite in the material under study, a negative result indicates that it is absent.

Carrying out parasitic methods of diagnosing toxoplasmosis has a number of peculiarities: firstly, there is a possibility of a false negative result due to the fact that the parasites have already settled in the tissues of organs and are not located in a specific section of the studied material. And secondly, pathogens in case of non-observance of all necessary conditions may die in the material taken for analysis even before the microscopy, which will also negatively affect the result of the study.

Diagnosis of toxoplasmosis in utero

When confirming the infection of a pregnant woman, the question of intrauterine infection of the fetus arises - additional diagnostics are needed. The analysis of toxoplasmosis analyzes by intrauterine methods is based on the detection of fetal development pathologies, as well as the direct determination of parasites in the amniotic fluid. There are such methods of intrauterine study of toxoplasmosis:

1. Ultrasound diagnosis - allows to detect abnormalities in the development of the fetus, namely violations such as a decrease in the thickness of the placenta, the detection of calcinates in the brain tissue of the fetus, ascites and hepatomegaly, which may indicate the penetration of the pathogen from the mother to the fetus.
2. Amniocentesis, or the study of amniotic fluid - is carried out by PCR diagnostics of toxoplasmosis.

Methods of diagnosis in complicated medical cases

With complicated forms of infection or the inability to use common methods of diagnosing toxoplasmosis, such methods of disease detection are used:

1. Subcutaneous test with toxoplasmin. The drug is injected. Evaluate the result after two days. If there is swelling, whose diameter is not less than 10 mm, then the sample is considered positive. Such an analysis does not answer the question of whether the disease is acute or there is a long-standing infection.
2. Instrumental methods help to identify specific disorders and abnormalities in the work of internal organs, characteristic of the parasite-causative agent of toxoplasmosis. Apply methods such as ultrasound, computed tomography, magnetic resonance imaging, biopsy. Only the specialist can decipher the result of such diagnostic procedures.

In most cases, doctors prescribe a standard blood test for toxoplasmosis. The interpretation is carried out by ELISA or PCR. In controversial cases, additional tests and examinations are recommended. Often, for the correct interpretation of the results, it is necessary to take into account a whole range of medical factors affecting the formulation of the final diagnosis. Therefore, do not solve the results yourself, but seek professional help from a specialist.