Analysis for tuberculosis by blood in children and adults - indications for conduction, preparation, decoding results

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What is tuberculosis

Severe infectious disease occurs in chronic form. Tuberculosis causes bacteria - a rod of Koch( Mycobacterium tuberculosis complex), which are resistant to external influences. Characteristic features of this disease:

  • are affected by respiratory system - pulmonary form;
  • suffer joints, bones, lymph nodes, genitourinary system - extrapulmonary appearance;
  • infection often occurs by airborne droplets, less often by contact, through food, from mother to fetus via the placenta.

In tuberculosis, an open and closed form of development is distinguished. In the first case, the patient is contagious, dangerous to others, is the carrier and excretory of bacteria. He is treated in special dispensaries. When the form is closed, it looks like a cold, dangerous microbes are not released into the environment. Infection is characterized by the appearance of such symptoms:

  • depressed mood;
  • chills in the evening;
  • subfebrile temperature;
  • increased sweating at night;
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  • enlarged lymph nodes;
  • appetite disorder;
  • restless sleep;
  • weakness;
  • cough;
  • weight loss;
  • tachycardia.

It is generally accepted that people who are in poor social and living conditions with a low standard of living are ill with tuberculosis. Doctors believe that the main factor in the appearance of infection is a decrease in immunity. Tuberculosis bacillus, penetrating into the body, can stay there for a long time, becoming active after a sharp fall of the body's defenses. Provoking reasons for the development of pathology often become:

  • stressful situations;
  • pregnancy;
  • defective food;
  • chronic diseases;
  • alcohol abuse;
  • HIV infection;
  • addiction;
  • smoking.

Analysis of blood for tuberculosis

The primary methods of diagnosis of infection include the Mantoux reaction, which is carried out in childhood, and fluorography for adults. More accurate and informative is the analysis for tuberculosis by blood. Such a technique has advantages:

  • there are no contraindications;
  • diagnosis is established in a short time;
  • there is no need to conduct repeated studies;
  • false positive results are excluded;
  • replaces the Mantoux test with the child in the presence of prohibitions for its conduct.

What tests should be given to a patient in case of suspected tuberculosis infection, the doctor decides, taking into account the clinical picture. There are several types of studies that are used at different stages of the disease. Among the very first and mandatory methods:

  • general blood test - determines the presence of an inflammatory process in the body;
  • biochemical study - on the changes in proteins in the blood structure reveals the form and stage of the disease.

To clarify the diagnosis of tuberculosis, additional types of blood tests are performed. Doctors prescribe to patients:

  • PCR - polymerase chain reaction - is informative, in a short time gives a complete picture of the development of the disease, is used in the case of extrapulmonary infection, for early diagnosis, treatment control.
  • ELISA - enzyme immunoassay - determines the blood content of specific antibodies to the causative agent of the infection - the Koch shelf.
  • T-SPOT - a modern research method, used in HIV infection, characterized by accuracy.

When it is necessary to do an analysis of

Children are at risk for developing tuberculosis lesions. In addition, they have not fully formed the immune system, the disease can adversely affect all the functions of the body. The analysis for tuberculosis by blood is carried out:

  • to children who have been in contact with sick people;
  • to babies who have mixed results after a Mantoux test;
  • for citizens entering work in children's medical and educational institutions( kindergartens, schools).

Indication for the study is contact with the carrier of the disease. To hand over a blood on a tuberculosis demand from wishing to work at public catering establishments. Analyzes are prescribed for suspected pathological processes or for confirmation of tuberculosis infection when the patient is observed:

  • shadows in the image during fluorography, radiography;
  • rise in temperature in the evening;
  • weight loss;
  • chronic cough;
  • sweating at night;
  • strong weakness;
  • lack of appetite;
  • restless sleep with nightmares.

General blood test for tuberculosis

There are no special markers that help to detect this infectious disease. Clinical analysis of blood in tuberculosis reveals the presence of inflammation and pathological processes in individual stages. When decoding it is noted that in the case of development:

  • infiltration( the initial stage of the disease) - increases in ESR( the rate of erythrocyte sedimentation), leukocytes vary little;
  • disseminated form( widespread) - observe a significant deterioration in performance;
  • process remediation - the results come back to normal.

A general blood test is performed in the laboratory. The patient is sampling the biomaterial for finger research. The results are ready in a few hours. Minus this method - you can not put an accurate diagnosis. Important indicators for decoding the results:

  • ESR in tuberculosis - 80 mm / h, which indicates an active inflammatory process. The normal value for women is 20 mm / hour, men - 15;
  • the number of leukocytes - note the excess( norm - 4-9 x10 in 9 degrees / l);
  • lymphocyte count decreased;
  • increased the number of eosinophils - up to 8%( normal for adults 0-5).

When deciphering a general analysis for tuberculosis by blood, attention is drawn to the deviation from the erythrocyte norm. This indicator depends on the nature of the disease:

  • with a sluggish form, pinpoint localization of the lesion, the amount is normal, but their color changes, the level of hemoglobin in the erythrocyte decreases;
  • with a significant infiltration - reduce the size of red blood cells and their number.


When performing this study, blood is taken from the vein, the result is obtained the next day. With the correct interpretation of the indicators, you can identify serious diseases at an early stage. Unfortunately, the biochemical analysis of blood in tuberculosis does not provide an accurate diagnosis. The study pursues the following objectives:

  • periodic monitoring of the treatment process;
  • correction of homeostatic disorders( ensuring the stability of the internal environment of the body);
  • revealing the effects of drugs, side effects.

In case of tuberculosis, the biochemical parameters of the blood depend on the stage of the disease, complications, concomitant pathologies. When analyzing the analysis, note:

  • when the infection is inactive, the total protein, protein fractions of blood serum are normal;
  • in the acute course of the disease, in the case when the chronic form of tuberculosis infection begins to progress, the albumin-globulin coefficient decreases( norm 15, -2.3).

Biochemical research in the development of bacterial infection helps in the dynamics to monitor the liver and kidneys. To assess the patient's well-being, especially when the disease is severe, pay attention to such indicators of blood in tuberculosis:

  • direct and total bilirubin( below the norm);
  • AST - aspartate aminotransferase( increases);
  • ALT - alanine aminotransferase( increased).


With the help of this method, studies quickly determine the presence in the blood of specific antibodies to the causative agent of tuberculosis - the Koch stick. ELISA - enzyme immunoassay - is used as an alternative to the Mantoux test. The results are ready in two hours. When conducting research in the laboratory:

  • in a patient produces blood from a vein;
  • biomaterial is treated with a special solution;
  • is expected to form a link between the antigen and the antibody;
  • with a positive result fixes the reaction of the enzyme.

The lack of analysis of ELISA - in the absence of accuracy by 100%, the impossibility of determining the stage of the disease. It is not impossible to receive false positive and false negative results. Detected antibodies to tuberculosis do not always indicate a disease. A negative result is not necessarily absence of infection. Immunoglobulin Amg is not found in the study in the case of:

  • of the initial stage of infection, when it has not yet been developed in sufficient quantity;
  • the patient has an immunodeficiency state.

Positive result - the presence of tuberculosis in immunoglobulin assays Amg. It can talk about such processes in the body:

  • found an active form of the disease, which is not large-scale;
  • immunoglobulins appeared as a result of the recent vaccination of a child from tuberculosis, or a transferred illness( false positive result);
  • marked significant shifts in treatment;
  • the patient is sick with tuberculosis.

PCR Diagnosis

The method of polymerase chain reaction( PCR) is prescribed by doctors if there is a diagnosis and needs to be confirmed. With this analysis, the blood becomes not only blood, sputum, urine, spinal fluid, swabs of genital organs and throat are examined. Advantages of this technique:

  • high accuracy;
  • diagnosis of the disease during the day;
  • accurate detection of the focus of infection in extrapulmonary form;
  • revealing the pathogen, even one molecule at an early stage of the disease;
  • the right choice of treatment technique;
  • monitoring the results of therapy.

There are no contraindications for this study. It is used to diagnose infection in children, pregnant women. The lack of PCR diagnostics in its complexity. High qualification of specialists in the laboratory is required. The study is carried out in this way:

  • makes blood sampling from the vein;
  • is placed in a flask with a special substance that stops the clotting process;
  • cells isolate from plasma;
  • with the help of a polymerase reaction isolate the DNA of the pathogen;
  • the presence of even several molecules of the Koch sticks is evidence of the development of the infectious process.

T-SPOT analysis

This is one of the most advanced, high-precision methods for diagnosing tuberculosis. To conduct a study, blood sampling is made from the vein, and the immune system responds to the presence of microorganisms. Bacterial tuberculosis contains specific antigens. They respond to immunity - there is activation of lymphocyte cells, the presence of which is fixed in the study. T-SPOT.TV is the international name of the method, which stands for:

  • T - immune cells;
  • SPOT - spot;
  • TV - the designation of tuberculosis.

During the study, spots that are formed in place of antigen-specific immune cells are counted. The analysis reveals all forms of the disease. Minus such a study - it is impossible to distinguish the active phase of infection from latent( latent).The positive aspects of performing the T-SPOT technique:

  • high accuracy;
  • no contraindications;
  • possibility of conducting research in people with allergies, pathologies that affect immunity( diabetes, HIV infection);
  • no false positive results;
  • receiving totals within half an hour.

Blood test for tuberculosis for a child

In childhood, tuberculosis( Mantoux) is used to detect tuberculosis for prophylaxis. If the result is positive, additional tests are prescribed. In the complex diagnosis of an infectious disease, a general blood test is used. Decoding is carried out on the same principles as in adults. The indicators depend on the age, the inflammation is indicated by the following values:

  • ESR - increase( norm 4-10 mm / hour);
  • leukocytes - increase( more than 4-8,8 x10 in 9 degrees / l);
  • hemoglobin is downgraded;
  • the number of neutrophils( unripe leukocytes) exceeds 6%.

In case of an allergic reaction to Mantoux, an alternative, modern, highly sensitive blood test for tuberculosis in children is performed - QuantiFERON-TB Gold7.With its help determine the activity of the infectious process, reveal the latent form of the disease. Among the effective methods of diagnostic testing for tuberculosis by blood in children noted:

  • enzyme immunoassay - reveals antibodies to the bacteria that caused the infection;
  • polymerase chain reaction - with high accuracy determines the tubercle bacillus Koch by the presence of their DNA in the blood.


A dangerous infectious disease requires not only timely diagnosis, but also periodic monitoring of the results of treatment. With tuberculosis, blood tests are considered informative methods. What methods of research are used in this case, how do they differ? In the review of blood test methods you can learn about the features of the analysis, information, the speed of obtaining results.