Useful Tips

Diagnosis of tuberculosis: blood test, Mantoux test, diaskin test and others

Pin
Send
Share
Send
Send


Mantoux Testing Technique

The technique for conducting a mantoux test consists in introducing a special substance, tuberculin, obtained from destroyed tubercle bacilli into the upper layers of the skin of the person being examined. Typically, a sample of the skin of the forearm is selected for the test. If a person has contracted a tuberculosis infection, then the injected tuberculin is recognized by the human immune system as a sign of a tuberculosis infection. In this case, at the injection site of tuberculin, a focus of allergic inflammation occurs (papule, button, plaque, infiltrate). If a person has not met a tubercle bacillus before, then tuberculin is “not familiar to him”. In this case, there is no reaction to the Mantoux test - the result is regarded as negative.

The Pirke test (a type of tuberculin test) involves the cutaneous application of tuberculin (through a scratch). From an infectious and toxicological point of view, tuberculin is a safe substance.
The Mantoux test technique involves strictly intradermal (intradermal) administration of a certain amount of tuberculin (usually 2 tuberculin units “TE”, which corresponds to 0.1 ml of solution). At the injection site of tuberculin in case of a positive reaction, a focus of inflammation occurs (papule, swelling, inflammation). The size of the papule allows us to judge the tension (activity) of anti-tuberculosis immunity (see Evaluation of the results of the Mantoux test below). Before evaluating the results, it is recommended to avoid any effects on the papule (washing, combing, lubricating with iodine, brilliant green, applying a bandage, adhesive plaster, etc.) as this may affect the accuracy of the test results.

The principle of operation of the Mantoux test

The principle of action of the Mantoux test is to provoke an inflammatory and allergic reaction with the help of a specific substance of tuberculin, a structural component of Koch's rods (pathogens of tuberculosis, mycobacterium tuberculosis).

The Mantoux test works like this:
If a person has ever had contact with tubercle bacilli, then in his body there are cells of the immune system (lymphocytes) that have “remembered” these microbes and are ready for a new meeting with him. This is the essence of immunity: most infections are remembered by the body's immune system. Due to this, during a new contact with the infection, the immune response is faster, more powerful, consistent and therefore more effective, and the disease stops at the very beginning of its development.
In relation to tuberculosis, activated lymphocytes (cells of the immune system) memorize the structure (protein) of mycobacterium tuberculosis and, when they meet it again, they launch a powerful immune response designed to destroy foreign material.
The Mantoux test allows you to evaluate three possible conditions of human anti-tuberculosis immunity: normal immunity, lack of immunity and excessively activated immunity.
If a person has been in contact with tuberculosis pathogens (for example, during vaccination or had an infection that has not turned into a disease), then the tuberculosis immunity is in a state of normal activity, and a new contact with tuberculosis pathogen proteins (tuberculin) is accompanied by a moderate inflammatory response (in place) injection of tuberculin (see below) a small papule appears with a slight swelling and inflammation). This suggests that the immune system of this person is known for tuberculosis bacteria, and she is ready to fight them.
If a person has never come into contact with tuberculosis bacilli and has not received a vaccine for tuberculosis (or received a vaccine for a very long time), then the introduction of tuberculin does not cause any inflammatory reaction, since there are no cells in the body that can respond to this signal, in other words, the body does not respond to an unfamiliar infection.
If a person has suffered a recent infection with tuberculosis bacilli or there is an active tuberculosis process in his body (in other words, if a person is ill with tuberculosis), then there is a very large number of extremely active lymphocytes in his body that are specially designed against tuberculosis bacilli and the introduction of tuberculin triggers a powerful inflammatory reaction, whose strength is reflected in the size of the papule.

Assessment of the results of the Mantoux test

Evaluation of the results of the Mantoux test (reaction) is carried out 72 hours (3 days) after the injection of tuberculin: a doctor (trained nurse) examines the injection site and measures the size of the papule in millimeters. The table below provides an assessment of the results of the Mantoux test based on the size of the papule (seal):

Result

Papule sizes

Papule Description

The meaning of the result and its possible cause

What to do?

Negative

Lack of any consolidation, a point wound from a needle

Lack of tuberculosis immunity.

TB vaccination needed

Falsely negative *

( a negative Mantoux test in individuals infected with Koch's bacillus )

Energy is a significant weakening of the immune system,

Tuberculosis infection has occurred recently (up to 10 days),

Small age of the child - less than 6 months.

If there are complaints, clinical symptoms, changes with other research methods, a physical examination is necessary. In some cases, it is necessary to repeat the Mantoux test after 10 days and consult with an immunologist.

Doubtful

Only redness without compaction

Evaluation of the status of anti-tuberculosis immunity is difficult, anti-tuberculosis immunity is very weak.

Consultation of a pediatrician in order to resolve the issue of the need for consultation of a TB doctor

Positive

The formation of plaques (seals) at the injection site.

The normal state of immunity after vaccination. If vaccination has not been given, infection is possible.

Consultation of a TB doctor and conducting Diaskintest

False positive *

( positive Mantoux test in individuals not infected with Koch )

Tuberculin allergy,

Infection with non-tuberculous mycobacteria.

Consultation with a TB doctor and immunologist and conducting Diaskintest

Hyperergic

³ 21 mm in adults

Large papule, “bubble” in the injection zone, the formation of daughter papules, enlarged lymph nodes (lymphadenitis).

Increased Tuberculin Reactivity

Mandatory consultation with a TB doctor and allergist

"Turn" Mantoux test

Strengthening sample results compared to last year.

A positive test after a series of negative results,

Strengthening last year’s reaction by 6 mm,

Papule ³12 mm 3 years after BCG vaccine.

Such a result, with the exception of all factors capable of distorting the Mantoux test, indicates that over the past year the body suffered infection with tuberculosis.

Mandatory consultation with a TB doctor

Factors That Can Distort Mantoux Test Results

· Acute and chronic infectious diseases

· Technique for performing and reading the Mantoux test

· Important! Tuberculin injection site with a Mantoux test can be wet and this does not distort the test results. Do not injure mechanically (e.g. rub with a towel roughly)

Indications for the Mantoux test

Mantoux test is carried out for:

· Identification of infection with tubercle bacillus

· Case detection of tuberculosis

· Checking the status of tuberculosis immunity and selecting a group for re-vaccination

Contraindications for conducting a planned Mantoux test

A scheduled Mantoux test can not be carried out in the case of:

· Diseases of the skin at the injection site

· Acute and chronic infectious diseases (Mantoux test is carried out one month after recovery)

Mantoux test and vaccination calendar

To avoid distortion of the results of the Mantoux test:

· Do not give any vaccinations on the same day as the Mantoux test

· Vaccinations can be given after evaluating the results of the Mantoux test

· If vaccinations were given before the Mantoux test, reliable results of the sample can be expected only 1 month after vaccination.

· The Mantoux test does not leave tuberculosis immunity and cannot replace the BCG vaccine.

Is it necessary and possible to take antihistamines before and after the Mantoux test?

Narrow-spectrum antihistamines (for example, suprastin) do not affect the results of the Mantoux test, since completely different allergic mechanisms that are not affected by antihistamines are involved in their manifestation.
In the case of an allergic background in a child (to avoid obtaining false positive results), antihistamines should be taken within 5 days before the Mantoux test, and then taken another 3 days before reading the result.

Elimination of false positive Mantoux test results using Diaskintest

Due to the fact that the positive results of the Mantoux test can be observed in people infected with non-pathogenic mycobacteria (bacteria similar to the causative agents of tuberculosis, but not able to cause tuberculosis), as well as in people (mainly in children) who have recently been vaccinated against tuberculosis (BCG) in all In cases of a positive Mantoux test result, Diaskintest is recommended.

The use of the drug Diaskintest for the diagnosis of tuberculosis, the state of tuberculosis and the exclusion of false positive Mantoux test results

Diaskintest is amodern method for the diagnosis of tuberculosis. Diaskintest involves injecting a small amount of a special solution into the skin of the person being examined, which contains proteins that are characteristic only of tuberculosis pathogens.
Diaskintest gives a positive result only in the case of people infected with tuberculosis, as well as in patients with tuberculosis. Diaskintest, gives a negative result in persons not infected and not suffering from tuberculosis, as well as after full recovery from tuberculosis. Diaskintest results also remain negative if a person has immunity after vaccination against tuberculosis (BCG) or if the examined person is infected with mycobacteria that cannot cause tuberculosis (false positive Mantoux test).
Diaskintest is a much more specific and effective method for diagnosing tuberculosis than the Mantoux test.

What is diaskintest?

Diaskintest is a method for diagnosing tuberculosis and conditions of tuberculosis, which is based on determining the reaction of the organism of the person being examined to special substances that are found only in microbes of tuberculosis pathogens. Diaskintest was developed at the Russian Research Institute of Molecular Biology of the Moscow Medical Academy. THEM. Sechenov. Preclinical and clinical studies conducted in strict accordance with all modern requirements have shown its high efficiency.

What are the advantages of Diaskintest compared to the Mantoux test?

Currently existing intradermal methods for diagnosing tuberculosis (Mantoux test and Diaskintest) work on the same principle: a small amount of a special solution containing substances that are found in the structure of tuberculosis pathogens is injected into the patient’s skin (most often on the forearm). The Mantoux test solution contains tuberculin, a special protein that is found in the causative agents of tuberculosis, as well as in their “close relatives”, bacteria used in BCG vaccination and non-pathogenic mycobacteria, which are very similar to the causative agents of tuberculosis, but unlike the latter, they cannot cause disease in humans.
Diaskintest formulation contains only recombinant ESAT6 / CFP10 proteins that are unique to tuberculosis pathogens.

Due to the different composition, the results of Diaskintest and the Mantoux test reveal two different aspects of the state of anti-tuberculosis immunity: a positive Mantoux test means that the body of the person being examined is familiar with tuberculin, which in turn may mean that the person being examined was in contact with a tuberculosis infection or recently received BCG vaccine, or infected with non-pathogenic mycobacteria, which can not cause disease and therefore do not require any treatment. The last two varieties of the Mantoux test result are called false positive.
Unlike the Mantoux test, Diaskintest gives a positive result only if the body of the person being examined is familiar with proteins that can only be found in the causative agents of tuberculosis. In other words, a positive result of Diaskintest with a high degree of accuracy indicates that the person being examined is either infected with tuberculosis at the moment, or already has it.

Thus, Diaskintest in comparison with the Mantoux test:

· Allows you to get an accurate result and distinguish the state of tuberculosis infection from false positive reactions in people vaccinated with BCG and people infected with non-pathogenic mycobacteria

· Has a high sensitivity: all patients infected with tuberculosis and tuberculosis who can become ill with tuberculosis in the near future give a positive reaction to Diaskintest

· Makes it possible to judge the effectiveness of the treatment of tuberculosis: for all people who have recovered after tuberculosis, the result of Diaskintest is negative

Mantoux positive reaction - what to do?

In the case of a positive reaction of the Mantoux test (see Mantoux test - reading the results), it is necessary to find the opportunity to conduct a second examination using Diaskintest in order to exclude false positive Mantoux results and avoid the need for preventive treatment.

Diaskintest technique

The injection of the drug for Diaskintest is carried out exactly as with the Mantoux test: strictly intradermally, in the region of the middle third of the forearm, with a thin needle.
Often, Diaskintest and the Mantoux test are carried out simultaneously (on different hands), which makes it possible to identify false positive Mantoux reactions.

How is the reading of Diaskintest results?

Diaskintest results are read after 72 hours from the moment of injection. The doctor evaluates the diameter of the red spot (hyperemia) and seals (papules) that formed at the injection site. Diaskintest results may be

1. negative - in the absence of a red spot or seal at the injection site

2. doubtful - if there is only a red spot at the injection site or a slight swelling with a diameter of less than 2-4 mm

3. positive - if there is swelling at the injection site with a diameter of 5 mm or more,

4. hyperergic: with the formation at the injection site of a seal with a diameter of more than 15 mm or more, as well as in the case of the appearance of bubbles at the injection site, ulceration or enlargement of the lymph nodes in the ulnar fossa or in the armpit.

All individuals who have been identified with a dubious, positive, or hyperergic reaction to Diaskintest need additional testing for tuberculosis.

When can Diaskintest not be performed?

Diaskintest in a planned manner cannot be carried out in case of

· Acute and chronic infectious diseases occurring with fever: acute respiratory viral infections, pyelonephritis, pneumonia, bronchitis, etc.

Exacerbation of diseases of internal organs (hepatitis, colitis, pancreatitis, pyelonephritis, etc.) the presence of skin diseases in the acute phase (atopic dermatitis)

Recent exacerbation of allergies

In patients with epilepsy (especially in case of poor seizure control)

Can Diaskintest provoke tuberculosis?

Diaskintest preparations are obtained from genetically modified strains of Escherichia coli, which in no case can cause the development of tuberculosis.

Diaskintest is usually well tolerated, only in rare cases there is a short-term and insignificant increase in temperature, mild headache and malaise.

Diaskintest and vaccinations

The interval between Diaskintest and previous preventive vaccinations (including BCG) should be at least 1 month. After setting diaskintest vaccination is possible after reading its results.

Methods for the diagnosis of tuberculosis

In Russia, two methods are used for screening a population for tuberculosis:

  • in children - the Mantoux test (it is advisable to supplement it with Diaskintest or the Quantiferon test),
  • in adults - fluorography of the lungs.

According to the results of these tests, doctors select contingents of citizens for further clarifying diagnostics. In addition, if a person presents complaints specific to tuberculosis, he is also shown a more detailed examination. With a tuberculosis infection, the patient may complain of:

  • prolonged cough
  • weight loss
  • constant subfebrile condition (when body temperature is always slightly increased),
  • baseless weakness
  • swollen and tender lymph nodes
  • night sweats.

Patients with suspected tuberculosis should be referred to a TB specialist who, after examination and discussion, will draw up a plan for further examination. К диагностическим процедурам, позволяющим подтвердить этот диагноз, относят:

  • Рентгенографию легких.
  • Микробиологическое исследование патологического материала.
  • Analysis of urine, sputum, blood and other body fluids on tubercle bacillus DNA using PCR.
  • A blood test for antibodies to the causative agent of tuberculosis.
  • Histological examination.

Blood test for tuberculosis

The following blood tests are used to detect tuberculosis infection:

Quantiferon Test - A new method for the diagnosis of tuberculosis, which is considered as a good alternative to skin tests - the Mantoux test and Diaskintest. The method is based on the determination of specific interferons in the venous blood of the subject, which appear only when pathogenic strains of mycobacteria enter the body. The types of microorganisms used in the BCG vaccine, as well as non-tuberculous mycobacteria do not cause the formation of these interferons. Thus, false positive test results associated with post-vaccination immunity are excluded. The quantiferon test makes it possible to detect infection with tubercle bacillus, but does not distinguish latent (dormant) tuberculosis from active.

PCR blood test for tuberculosis - the most accurate study (reveals even a small amount of genetic material of the pathogen in the blood serum). In addition to blood, DNA fragments of tubercle bacillus can be found in the secretion of the prostate, urine, joint fluid, cerebrospinal fluid, menstrual blood, sputum, and effusion. That is, using PCR, it is possible to more accurately establish the localization of the tuberculosis process.

Serological examination for tuberculosis - An enzyme-linked immunosorbent assay for specific antibodies (immunoglobulins of different classes) that synthesize the immune organs in response to infection. Detection of anti-TB antibodies indicates the presence of tuberculosis infection. In turn, the absence of antibodies does not always indicate that there is no tuberculosis. In the initial stages of the disease, immunoglobulins may not be enough for analyzers to detect, in addition, many patients suffer from immunodeficiency, which also interferes with normal antibody formation. If a child has recently been vaccinated against tuberculosis, the result of this test may be false positive.

Interpretation of blood tests for tuberculosis must be carried out taking into account the clinical picture and the results of other examinations. The only way to identify the active form of the disease, which is dangerous and requires serious treatment.

Mantoux test and Diaskintest

Mantoux test or tuberculin diagnostics is an allergic skin test for tuberculosis, which consists in introducing tuberculin into the thickness of the skin of the patient's forearm - a mixture of tubercle bacillus antigens. The main objectives of this study:

  • Establishment of a possible tuberculosis infection.
  • Identification of indications for vaccination against tuberculosis. If the Mantoux test is negative, children must be vaccinated.

Mantoux tests are required for all children after 12 months of age.. This test is not for allergy sufferers. Acute infectious diseases, exacerbated chronic ailments, inflammatory processes on the skin are temporary contraindications for the Mantoux test. Doctors call low specificity a big drawback of tuberculin diagnostics - with this test, you cannot distinguish between post-vaccination and infectious (which is present during infection) allergies to tuberculin.

The results of the Mantoux test (which are read 72 hours after the introduction of the diagnostic drug) may be as follows:

  • Negative - the skin is clean, there is only a trace from an injection.
  • Positive - at the injection site there is a seal with a diameter of 5-16 mm.
  • Doubtful - only redness of the skin is noted or a very small seal is felt.
  • Hyperergic - the diameter of the seal exceeds 16 mm.

A sign that the child is supposed to be vaccinated against tuberculosis is a negative or doubtful result of the Mantoux test. But if a negative result becomes positive or a hyperergic reaction develops, the patient needs a TB consultation - infection with tuberculosis is possible.

Diaskintest - A fairly new method for the diagnosis of tuberculosis, which is also essentially an allergic skin test, but has a higher specificity than the Mantoux test. The dose of a diagnosticum introduced into the skin contains antigens of only virulent tubercle bacilli. In this regard, Diaskintest can be used to assess the activity of tuberculosis.

Diaskintest can not be used instead of a Mantoux test to select children for vaccination or revaccination against tuberculosis.

The method of conducting Diaskintest is the same as with tuberculin diagnostics. The study is carried out in specialized tuberculosis hospitals, the results of the test are read by the TB specialist after 72 hours.

Microbiological examination for tuberculosis

The following microbiological methods are used to diagnose tuberculosis infection:

  • Microscopy of smears.
  • Bacteriological examination of pathological material.

These methods allow you to identify the causative agent of infection in various body media (urine, bowel movements, cerebrospinal fluid), pathological discharge (sputum, effusion) and thereby confirm the diagnosis.

The easiest way to detect tubercle bacillus is microscopy. It can be ordinary and luminescent. In the first case, pathological material is applied to a glass slide, then it is processed according to a special technique with various reagents and examined under a microscope. Under luminescent microscopy, the material is also treated with chemicals, and a glass slide is examined under a microscope equipped with a luminescent backlight.

Bacteriological study for tuberculosis - This is a more complex study in terms of the technique, however, it allows you to isolate a pure culture of the pathogen and determine the sensitivity of the bacteria to drugs. The first results of this analysis can be obtained only a few days after sowing.

X-ray diagnosis of tuberculosis

There are two methods for radiological diagnosis of tuberculosis infection: fluorography and radiography of the lungs. The first method is used for mass examination of the population, the second - for a more detailed diagnosis of lung conditions. The difference between radiography and fluorography is the size of the images, their clarity and, accordingly, information content.

According to a qualitative x-ray picture, the doctor can diagnose some forms of primary tuberculosis (primary tuberculosis complex, damage to the lymph nodes of the chest) and secondary pulmonary tuberculosis with an exact determination of its stage: focal, infiltrative, etc.

Histological examination for tuberculosis

This study is resorted to in controversial cases when it is necessary to clarify the nature of lung tissue damage and exclude other diseases. For analysis, the material is taken using endoscopic equipment through the bronchi or using a special needle transthoracically (piercing the chest). In some cases, histologists examine the sputum secreted by the patient. If the lungs are not infected with tuberculosis, histological analysis may also shed light on the nature of the pathological changes. For this, material for research is taken from the affected organ.

From the information presented it is clear that screening for tuberculosis cannot be limited to the use of any one diagnostic method. An X-ray, a Mantoux test, or a blood test alone cannot be an accurate diagnosis. Information about the patient (contacts with a patient with tuberculosis, living conditions, the presence of concomitant diseases), clinical data and the results of a comprehensive instrumental and laboratory study must be taken into account.

Zubkova Olga Sergeevna, medical observer, epidemiologist

6,789 total views, 6 views today

Key points

  1. You should expect that you will have a strong blow at the injection site of the tuberculosis skin test.
  2. Your doctor will measure a stroke called a seal to determine the likelihood of having TB.
  3. Your results will depend on your risk factors.

Tuberculosis (TB) is a highly contagious disease. It is caused by a bacterial infection called Mycobacterium tuberculosis ( Mtb ) Impact Mtb can lead to latent tuberculosis, which means that you are infected, but do not have any symptoms. Hidden TB can ultimately become active tuberculosis, for which medications must be treated.

There are two types of tests used to diagnose tuberculosis: a blood test and a skin test. Your test results will not reveal if you have latent or active tuberculosis. Instead, they are used to determine who should be treated and what type of medication.

What happens during a skin TB test?

The cutaneous TB test is also called the Mantoux Tuberculin Test (TST). The test is usually well tolerated, and people rarely have a negative reaction to it.

Skin tuberculosis testing is carried out in two parts. During one visit to the doctor’s office or clinic, a tiny amount of tuberculin is injected into the skin, usually in the forearm. Tuberculin is a sterile extraction purified protein derivative derived from tuberculosis-causing bacteria. After taking the injection at the injection site, a small pale stroke is formed.

The second phase of the test passes through 48-72 hours. At that time, your doctor will look at your skin to see how it reacts to tuberculin. Your skin reaction will help your doctor determine if you have been infected with tuberculosis. If you wait more than 72 hours, you will have to start a new test and a new injection.

Identification

Within a few hours after the injection, your skin around the injection site will begin to swell and harden. This stroke or compaction, as it is called clinically, will also turn red. The size of the seal is used to determine your results. The seal should be measured across the forearm, perpendicular to the axis between your arm and elbow. Several factors influence the interpretation of the test.

Attenuation sizeResult
less than 5 mmnegative for TB
not less than 5 mmpositive if:
• you recently had contact with someone with tuberculosis
• you have HIV positive
• you had an organ transplant
• you are taking immunosuppressants
• you previously had TB
not less than 10 mmpositive if: • you recently immigrated from a country with a high incidence of tuberculosis
• you live in high risk
• you work in a hospital, medical laboratory or other high-risk environment
• you are a child under 4 years old
• you used injecting drugs
15 mm and more
positiveA seal of less than 5 millimeters (mm) is considered a negative test result. If you have symptoms or know that you had a person with TB, you may be asked to take another test.

If the seal is at least 5 mm, this will be considered positive in people who:

had recent contact with a person with tuberculosis

  • were HIV positive
  • , had an organ transplant If you are taking medication with immunosuppressants or you have previously had tuberculosis, a 5 mm seal can also be interpreted as a positive test.
  • A seal of at least 10 mm can be considered a positive test if you are a recent immigrant from a country with a high prevalence of tuberculosis or you live in high-risk settings such as a nursing home. The same is true if you work in a hospital, medical laboratory or other high-risk environment, or if you are a child under 4 years old. A 10 mm seal can also be considered positive in people who inject drugs.

A seal of 15 mm or more is considered positive in any case, even if you do not think that you have been exposed to people with tuberculosis.

What does a positive test mean?

If you have a positive test result and you have symptoms or are at high risk of contracting TB, you will probably be prescribed medications to clear the infection and alleviate the symptoms.

If you have a low risk and have a positive test, your doctor may recommend a blood test for tuberculosis to confirm the diagnosis. A TB skin test is less accurate than a blood test, so you may have a positive skin test and a negative blood test.

If you recently received the Calmette-Guerin Bacillus (BCG) vaccine, which is used to reduce the risk of developing TB in humans, you may have a false-positive skin test result. Other reasons for a false-positive result include improper use of the test, inaccurate interpretation of the results of your test or infection with non-fungal mycobacteria.

You can also get a false negative result, that is, the test is negative, but in fact you are infected with tuberculosis. Again, improper administration of the test or interpretation of the result can lead to a false negative test result. If you have been infected with tuberculosis in the last few weeks, you may not have tested positive for tuberculosis. Babies, even if they have TB, may not always have a positive skin test.

If a false-negative result appears, but your risk of contracting TB or your symptoms indicates that you have an infection, a second skin test can be done right away. A blood test can also be done at any time.

You will have symptoms if you have active TB disease. Having only TB infection will not cause any noticeable symptoms.

One of the most common symptoms of tuberculosis is a cough that will not go away. You can also cough up blood. Other symptoms include:

  • night sweats
  • weight loss
  • decreased appetite
  • These symptoms can occur in many other conditions, so it’s important to get tested. Even a negative test is useful because it can rule out TB and help your doctor find the cause of your symptoms.
  • Advertising

A positive skin test is usually accompanied by a chest x-ray. Your doctor will look for white spots that indicate areas in which your immune system responds to bacteria. There may be other changes in the lungs caused by tuberculosis. Your doctor may decide to use computed tomography (CT) instead of a chest x-ray because a CT scan can provide more detailed information about your lungs.

What does T-SPOT.TB mean

The name T-SPOT.TB is deciphered as follows:

  • «T"Denotes T-lymphocytes (blood cells), based on the response of which a study is being performed. Stimulation of T-lymphocytes with special antigens characteristic of the causative agent of tuberculosis (Mycobacterium tuberculosis), contributes to the production of interferon.
  • «Spot"Translated from English, means" spot ". As a result of a laboratory experiment, spots form in the well, each of which marks a T-lymphocyte. Spot analysis counts the spots that have occurred on the site of immune cells specific for the tuberculosis antigen,
  • «TB"Is an abbreviated international designation for tuberculosis.

This analysis can be used for all people at risk for latent tuberculosis infection, as well as for people with suspected tuberculosis, regardless of their age, gender, immune status and therapy.

Pros (advantages) of the T-SPOT.TB test:

  • high specificity and high sensitivity,
  • lack of contraindications for research,
  • safety and lack of adverse reactions,
  • lack of false positive results in case of BCG vaccination,
  • the interpretation of the test results is less subjective than the interpretation of the results of skin tuberculin tests,
  • it can be used to differentiate tuberculosis infection in children from post-vaccination allergies, as well as to assess the level of specific immunity during treatment.

Cons (disadvantages) of the T-SPOT.TB test:

  • is not a legislatively fixed method for detecting tuberculosis, therefore it is done not for free, but at "your own expense",
  • the high cost of T-SPOT.TB (at least in Moscow - 6,000 rubles, an average of 6,800 rubles). In regions, the cost is much lower
  • the test can be done so far only in some cities: Moscow, St. Petersburg, Novosibirsk, Tyumen, Samara, etc.,
  • in some cases, the test gives a false negative reaction (100% diagnosis of tuberculosis does not exist).
  • T-SPOT is a way to quantify the presence of tuberculosis in the body, but the test does not distinguish between LTBI (latent tuberculosis infection) and active tuberculosis. Therefore, in regions with a high level of infection, the test does not have a direct diagnostic value.

Who is shown T-SPOT

T-SPOT can be used instead of a Mantoux test or Diaskintest test in all cases where skin tests are indicated as a test for the diagnosis of tuberculosis. As an additional research method to confirm or refute the questionable results of skin tests. And especially the test is shown to those whose имеются противопоказания к проведению пробы Манту и Диаскинтеста:

  • индивидуальная непереносимость туберкулина,
  • кожные заболевания и аллергические состояния в период обострения,
  • children, adolescents and adults with a high risk of developing an allergic reaction,
  • infectious diseases during exacerbation,
  • vasculitis,
  • epilepsy.

T-spot analysis. Research method

For the diagnosis of tuberculosis using a T-spot test take blood test in an amount of 2 to 8 ml, depending on age:

  • Children under the age of 2 years - 2 ml.
  • Children aged 2 to 9 years - 4 ml.
  • Adults and children aged 10 years and older - 8 ml.

For the study, venous blood is taken in the morning on an empty stomach (or at least 2-4 hours after the last meal).

The survey is carried out with the informed consent of the legal representatives of minor children.

T-SPOT Result

The result of the T-spot test can be:

  • negativeif there is no tuberculosis in the body,
  • positiveif the body is infected with tuberculosis,
  • doubtful (vague) if the test does not give a clear answer.

T-spot - a positive result:
“Positive” means a current infection, but does not allow to differentiate a recent tuberculosis infection from a previous one, and also to assess the degree of activity of the tuberculosis process. A positive T-SPOT involves the appointment of a CT scan of the chest to exclude local tuberculosis.

T-spot - negative result:
“Negative” more often means the absence of tuberculosis in the human body, but can also be observed with suppression of the T-cell link of the immune system that has arisen as a result of an immunodeficiency state, including with the progression of tuberculosis. In this case, one should focus on the results of direct research methods confirming the specific nature of the disease.

Negative test results in the absence of clinical symptoms of the disease allow the TB doctor to issue a certificate confirming that the child does not currently have active tuberculosis.

T-spot - dubious result:
In rare cases, test results cannot be interpreted due to failure to pass a positive test control and are assessed as uncertain. In this case, it is impossible not to confirm, not to rule out a tuberculosis infection.

T-SPOT.TB (T-SPOT®.TV) should be used and interpreted only in conjunction with the overall clinical picture. A negative T-SPOT does not exclude the possibility of infection with M. tuberculosis.

Comparison of tests for the diagnosis of tuberculosis

ParameterMantoux testDiaskintestQuantiferon TestT-SPOT (T-SPOT.TB)
ManufacturerRussian FederationAustraliaGreat Britain
Research methodSkin test (allergoprobe)Venous blood test
Adverse reactionsAre possibleRare but possibleNotNot
Contraindicationsthere isthere isNotNot
SpecificityLowHighHighHigh
False positive after BCG vaccinationYesNotNotNot
Dependence on the timing of vaccinationsYes
(not earlier than in 1 month)
NotNot
Interpretation of ResultsSubjectiveObjective

Pin
Send
Share
Send
Send