Many are interested in how a blood test for tuberculosis is taken and done. This procedure is quite common. This is a modern response to earlier types of diagnosis of the disease. But what are blood tests? What features do they include? And how should a citizen, based on the results, understand whether he has a disease or not? Understanding all this is not as difficult as it seems. It is not necessary to have a medical education in order to draw a conclusion on the finished results. So what knowledge should a citizen have in relation to tests for tuberculosis?
About the disease
First, what kind of disease are we talking about? The fact is that tuberculosis is a serious chronic disease, extremely dangerous and contagious. It is transmitted by airborne droplets or through household appliances. It is very common in the world, but in the initial stages, tuberculosis is quite difficult to detect.
This disease can affect all human organs. Therefore, it is impossible to accurately predict what the outcome will be. In order to recognize the disease in time, a set of studies is required. For example, do a blood test for tuberculosis.
The most common type of disease is the one that affects the lungs. It is with him that many associate. Quite often, the manifestation of the disease can be confused with the common cold. Tuberculosis alone does not manifest itself seriously. Especially in the initial stages of development.
Types of diagnosis of the disease
Many are interested in the name of a blood test for tuberculosis. Knowing this is important. After all, with timely treatment, the disease recedes, and the person does not face serious negative consequences of the disease. It is important to know that at the moment there are several types of diagnostics in the world.
Which ones? The following can be distinguished:
- Mantoux test;
- sputum analysis;
- bronchoscopy;
- IFA;
- QuantiFERON-TB Gold;
- IGRA;
- PCR
In some cases, a general blood test is performed. This is usually done in the initial stages to determine the likelihood of a disease. And confirmation occurs only through the methods indicated above. Now they have come up with another method that replaces a blood test with tuberculosis - diaskintest. It does not come in contact with blood, but it helps to detect tubercle bacillus in the human body. It has a number of advantages and disadvantages. It was introduced in Russia in 2016.
IFA
Now a little about blood tests. After all, they are considered the most informative. Most often, this term means an ELISA study. Such a blood test for tuberculosis allows you to detect the presence of antibodies to tubercle bacilli.
In principle, not the worst option. All the patient has to do is donate blood for analysis. Venous is usually taken; it provides a more accurate result. Unfortunately, it is generally accepted that ELISA is not too informative. Indeed, according to this study, it will not be possible to say at what stage the disease is, if any. But such a procedure helps, as already mentioned, to identify the presence of antibodies to the disease in the body.
Fortunately, medicine does not stand still and there are other ways to detect an ailment. Moreover, associated with blood. What pros and cons do they have? How are they carried out? How can we understand that a person is sick?
PCR diagnostics
Much more informative and effective is a PCR blood test for tuberculosis. This is a modern method that allows you to determine the presence of tubercle bacillus. It is extremely informative if sputum is not taken for the study.
Typically, PCR diagnostics are prescribed for suspicious symptoms that are somewhat reminiscent of tuberculosis. However, according to doctors, this study in the case of blood does not give 100% of the result. It is possible only when the patient is ill with tuberculous sepsis. Otherwise, PCR diagnostics of blood does not have high efficiency.
Mantoux
What else should you pay attention to? A blood test for tuberculosis in children, as a rule, is not performed. Most often, they are assigned the so-called Mantoux reaction. This technology allows with high, but not 100% accuracy to detect the presence of the disease.
How is the analysis carried out? A child is injected with a special preparation subcutaneously. Then for several days you need to watch the injection site. If there is no tuberculosis, then this area will remain unchanged. You can notice only a slight swelling and discoloration of the skin - it will become more pink.
In the presence of tuberculosis, the injection site swells, swells, the tumor begins to grow. Sometimes it can become cyanotic. In this situation, the child is reassigned to Mantoux. Either a blood test is done for tuberculosis (ELISA or PCR), which confirms or refutes the result of the sample.
Mantoux is sometimes mistaken
Nevertheless, it should be noted that the Mantoux reaction is far from the best way to diagnose tuberculosis in the body. The thing is that this analysis is often mistaken.
How else can you interpret the resulting analysis? Deciphering a positive Mantoux reaction is simple. It can be observed with:
- exacerbation of common chronic diseases;
- asthma
- allergies
- infectious diseases;
- weakened immunity;
- epilepsy.
Accordingly, even a positive test result does not give accurate indications of the presence of the disease. Therefore, a blood test for tuberculosis instead of Mantoux is more effective and informative. It is necessary to exclude all the previously listed scenarios. Only then will it be possible to judge the presence of the disease.
General blood analysis
If Mantoux is positive, do not panic. It has already been said that this diagnostic method is not the best. Need to take a blood test. With pulmonary tuberculosis (and not only), some changes in the body occur. Which ones?
The thing is that in the initial stages, the blood remains unchanged. Therefore, a general or clinical analysis does not make sense. Depending on the "neglect" of the disease, these or those indicators will change. A general blood test for tuberculosis sometimes really helps to verify the presence or absence of the disease.
Nevertheless, it is not worth relying on him. After all, blood and its composition change, depending on many factors. Therefore, it is recommended that either ELISA or PCR. But the general blood test should also not be forgotten.
Decryption for general analysis
What indicators should I look for if there is a chance of tuberculosis infection? With the active stage of the disease, a general blood test will really help to understand that the pathogen is in the blood.
How exactly? Fundamental is ESR. Normally, in humans, this indicator will depend on age. You should rely on the following data:
- children under 10 years old - up to 10 mm / h;
- women under 50 years old - up to 20 mm / h;
- women after 50 - up to 30 mm / h;
- men up to 50 years old - 15 mm / h maximum;
- after 50 - up to 20 mm / h.
Nevertheless, ESR in pregnant and sick people can increase. In tuberculosis, as a rule, this indicator increases to approximately 50 units or more. Therefore, you should pay attention to it. If the erythrocyte sedimentation rate in the blood exceeds significantly the norm, we can conclude that there is a high probability of infection.
Features of a blood test
What features should be considered if it is decided to conduct an additional study for the presence of the studied disease? A blood test for tuberculosis instead of Mantoux is prescribed quite often. But at the same time, ELISA and PCR are often not enough for a final diagnosis. A complete blood count also does not completely show the picture of what is happening in the body.
It should be noted that the doctor prescribes a biochemical blood test in case of suspicion of the presence of tubercle bacillus in the body. You can also do a separate study for the presence of protein. This will verify the results.
If there is tuberculosis, but only in an inactive form, then the protein indicator will be in the range of the norm. The acute form of the disease increases cholesterol, urea and lysozyme. In this case, albumin will be reduced.
A disease that affects the liver increases indicators such as AST, ALT, and bilirubin. All this is revealed by a blood test, while the Mantoux reaction does not provide such information. This fact must be taken into account.
Diaskintest
Now it’s clear that if there is any concern about the presence of the studied disease in the body, you can take a blood test for tuberculosis. Also, biochemistry and a general study are additionally prescribed. All this helps to comprehensively assess the situation and conclude that there is a disease in the body.
Nevertheless, now many are talking about a new type of diagnosis of tuberculosis, which allows not to contact the reagent with blood. We are talking about the previously mentioned diaskintest. This is a replacement for Mantoux. Is this study worth believing? What are the pros and cons of it?
This diagnostic method allows you not to contact with blood - this has already been emphasized repeatedly. So, with a weakened body, there is no likelihood of contracting the disease. For the patient, the diaskintest resembles Mantoux. Research is required annually. Usually every 12 months for people from 8 to 17 years.
True, many indicate that this type of body test for the presence of tuberculosis is not accurate. All this is due to the fact that, as in the Mantoux reaction, some factors can give a false positive result. And the person will be prescribed either a second study or a blood test for tuberculosis.
Conclusion
Now it’s clear how it is possible to identify the presence of a disease under study with the help of certain analyzes. QuantiFERON-TB Gold and IGRA are rare blood tests. Screenings that indicate the content of antibodies and the presence of the disease are themselves. In Russia, they are practically not used.
You may notice that even general and biochemical blood tests will help identify tuberculosis in a particular case. It is enough to pay attention to some indicators. They will be broken. ESR with tuberculosis necessarily increases. In general, only a doctor can make an accurate conclusion based on several studies. To confirm the diagnosis, you can take not blood, but sputum for analysis.