"Diaskintest" for children: from features of application to evaluation of results

A drug called Diaskintest is used in the diagnosis of tuberculosis. With its help, a skin test is performed, which can confirm the carriage of mycobacteria or active tuberculosis. It is often used as an alternative to the Mantoux test or to clarify its results.

Dosage form and composition

"Diaskintest" is a solution that must be administered intradermally. It is in a glass bottle in a volume of 3 ml, and one box contains 1, 5 or 10 bottles. The medicine itself is transparent, without any color.

The solution contains a recombinant protein that contains two antigens. This protein is obtained using modified E. coli, then diluted with a special buffer solution, to which a preservative (phenol) is added.

In addition, the preparation contains sodium chloride, sterile water and polysorbate 80, as well as sodium phosphate and potassium. The amount of the active ingredient in one dose of Diaskintest is 0.2 μg. In this case, one dose is 0.1 ml, that is, one bottle contains 30 doses.

The sample is done only in a medical institution, for example, in a municipal clinic, a private medical center or a tuberculosis dispensary. The drug from the opened bottle should be used within two hours.

The shelf life of "Diaskintest" is 2 years, and the solution must be stored at a temperature of + 2- + 8 degrees.

How does it work?

The protein present in Diaskintest is a tuberculosis allergen. The antigens it contains are found in pathogenic mycobacteria that cause tuberculosis. Thanks to these ingredients, injection with a solution helps to identify the immune response to the causative agent of tuberculosis.

After the introduction into the skin of a child infected with mycobacteria or sick with tuberculosis, a specific reaction occurs. It is referred to as delayed-type hypersensitivity. If the body is already "familiar" with mycobacteria, then the production of antibodies begins, which leads to the appearance of a small compaction (called a papule or infiltrate) or redness.

Since the preparation does not contain the pathogen itself, and only proteins isolated from mycobacteria are present, it is impossible to become infected with tuberculosis due to Diaskintest. In this regard, the solution is not at all dangerous.

Test accuracy

The sensitivity of the test is estimated at 78–96%, that is, in the presence of tuberculosis in 4–12% of patients, the test may turn out to be false negative. Most often this is due to immunodeficiency states, when immune cells do not respond to the injected allergen.

As for the specificity of the method, it is about 99%. This means that false positive results occur in about 1% of the subjects. They are caused by a reaction to other types of mycobacteria, not related to the causative agents of tuberculosis infection, which may be present in the body.

When is it used?

Diaskintest is recommended for detecting tuberculosis at any age. Children are prescribed such a test from one year. This test is used:

if there is a suspicion of tuberculosis (clinical symptoms are present) or there is a high risk of its development (there was contact with an open patient);
if a child was given a Mantoux test at school, it turned out to be positive, but there are doubts that this is an allergic reaction to BCG or to the components of the solution;
if a small patient has received a course of treatment against tuberculosis and it is required to determine how effective it was.

Since the use of Diaskintest is unable to confirm the immunity to tuberculosis developed after BCG, such a test cannot be used to select children who need revaccination. This "Diaskintest" differs from the Mantoux test, which is used to confirm immunity to tuberculosis. For this reason, it is not worth replacing Mantoux using Diaskintest.

For a more accurate diagnosis, it is recommended to combine such tests.

In addition, Mantoux shows tuberculosis at an early stage, and the test with Diaskintest will not be able to do this. And therefore, in situations where Mantoux turned out to be positive, but the Diaskintest made after it did not give a positive reaction, it is recommended to make another test after 2 months so as not to miss the beginning of the infectious process.

Contraindications

"Diaskintest" is not used if the child is ill with some kind of acute infection (he is coughing, he has a runny nose, high fever and other symptoms), as well as within 1 month after recovery. The solution is not used for any diseases with a chronic course, if they have worsened (first you need to treat such an exacerbation, and then make a test). An allergic condition is also a contraindication for such a drug, in which the symptoms of allergy are first eliminated and only then Diaskintest is administered.

Any skin disease in which there are pustules, rashes and other skin lesions in the forearm will also be an obstacle to performing the test. If a child visits an institution in which quarantine for chickenpox or other infection has been declared, Diaskintest is used only after the quarantine period ends.

If there is a risk that the child has contracted the flu or other acute respiratory infections, it is also safer to postpone the sample setting so as not to get a false positive result.

How is the test done?

The solution test is prescribed by the doctor, and the injection must be given by a qualified nurse who has the authority to perform intradermal tests. Diaskintest should be administered only intradermally - it is unacceptable to inject into a muscle or in any other way.

The solution is drawn with a tuberculin syringe, which has a thin short needle with an oblique cut. Before making a test, be sure to specify the date of manufacture and expiration date. Two doses of the drug are drawn into the syringe at once, after which the excess drug is released so that only 0.1 ml remains inside.

The child is in a sitting position during the injection. The injection is done in the forearm - in the middle third. First, the skin in this place is treated with alcohol, then it is pulled and an injection is performed, the result of which should be a papule. Normally, such a papule is pale, looks like a "lemon peel", and its diameter is 7-10 millimeters.

After the injection, the health worker must record in the documents exactly which drug was injected (its series, manufacturer, expiration date), when and where it was injected. Later, information about the sample result is added to this record.

If a child is prone to allergies or has any allergic diseases, Diaskintest should be administered in parallel with the use of antihistamines. Such medications are advised to start giving five days before the injection. Having made an injection, they are used for another 2 days after the test.

Another preparation for the introduction of "Diaskintest" is not needed.

How often can the test be done?

If you use "Diaskintest" to replace the Mantoux test, then the frequency will be the same, that is, once a year. If the child does not have BCG, more frequent examinations are recommended - every six months. The test should be done twice a year also for chronic diseases, for example, with lung diseases, stomach ulcers or diabetes mellitus.

If the result is negative, then it is allowed to re-enter Diaskintest after two months. If the test was positive, then you can repeat it at any time, when necessary.

Can I wash and wet my hand?

It is allowed to wet the injection site after the test. If the child was injected with "Diaskintest", he can swim, but it is better not to put any detergents on his hand, and also not to rub the injection site with a washcloth.

In addition, it is not recommended:

stick a plaster on the sample site;
wrap your hand with a bandage;
process the trace of an injection with brilliant green or other medicine;
lubricate the injection site with any cosmetic product;
scratch and rub your hand;
go to a bathhouse or sauna;
sunbathe in direct sunlight;
visit the pool or swim in a natural body of water;
engage in active sports;
stay in frosty air for a long time.

Such restrictions are due to the fact that due to high or low temperatures, contact with dirty water, cosmetics or sweat, the injection site of the allergen can become infected and inflamed, which will lead to an incorrect result.

When and how is the result checked?

The test with "Diaskintest" should be evaluated 72 hours after the injection. It is checked by either a nurse or a doctor, measuring the transverse size of the infiltrate. A transparent ruler is used for measurement, and the result is recorded in millimeters.

If there is no papule (infiltrate), but there is an area of redness, then the size of the hyperemia is measured. If the infiltration is present, but the skin around it is red, then hyperemia is not taken into account, but only the papule is measured.

What is the result?

The sample with "Diaskintest" is defined as follows:

negative - if there is no redness, and there is no papule at all;
positive - when there is an infiltration of any size;
dubious - if papules are not visible, but hyperemia is present.

If only a trace from the injection is visible on the child's hand, the dimensions of which do not exceed 2 mm, such a test is also considered negative.

What does the negative reaction say?

This result occurs if:

the child is not infected with mycobacteria;
the child was previously infected, but the infection is inactive;
the child was successfully treated for tuberculosis.

A negative reaction after a positive Mantoux test is probably a confirmation that the child reacted to Mantoux with an allergy or a false positive result of such a test was due to a recent BCG vaccination.

However, the absence of papules is not always a favorable sign. Any changes on the skin of the forearm after "Diaskintest" can occur in case of serious disorders of the immune function, when the infection is severe.

In addition, a negative reaction is possible at the very beginning, if the child has just become infected with mycobacteria, but his immune system has not yet responded.

Actions with a positive reaction

A positive result for "Diaskintest" indicates that the child's body has already "got acquainted" with mycobacteria. Depending on the size of the infiltrate, the positive reaction is divided into:

poorly expressed - if the papule is not more than 0.5 cm;
expressed moderately - if the diameter of the infiltrate is from 5 to 9 mm;
expressed - if the size of the papule is from 10 to 14 mm.

In the case when the infiltration is very large (its diameter is more than 15 mm), they speak of a hyperergic reaction. This is also the name of the presence of necrotic changes or a rash in the area of solution administration. If a child has inflamed lymph nodes or lymphatic vessels, these are also signs of a hyperergic reaction, even if the size of the papule is small.

If the reaction is assessed as positive, the child is sent for additional examination in order to clarify the diagnosis of "tuberculosis", because the test cannot accurately distinguish an active infectious process from a simple carrier.

To clarify the diagnosis, you need to pass blood and urine tests, do fluorography or x-rays of the lungs, ultrasound and other examinations. The same measures are taken in case of a questionable test result.

Side effects

Sometimes a nonspecific allergic reaction may occur to Diaskintest. Often it is represented by redness at the injection site, which occurs almost immediately after the test. By the time the result is assessed (on day 3), as a rule, such hyperemia passes and does not interfere with decoding. Other symptoms of solution allergy are: itching, redness of the conjunctiva, hives, swelling of the nasal mucosa, and so on. With such complications, an antihistamine should be given to the patient.

In some children, after the injection, the body temperature rises for a while, a headache appears, and the state of health worsens. This general reaction is rare and usually resolves on its own in a few hours (less often in a few days). From local negative reactions to "Diaskintest" can be identified edema, bruise or abscess.

If the injection site is swollen and begins to fester, you should immediately show the baby to the doctor, as this indicates bacteria entering the wound.

Drug interactions

Diaskintest does not affect the treatment with drugs that are taken by mouth. However, there are some limitations for such testing and prophylactic vaccination. If the child is to be vaccinated on schedule, then Diaskintest should be administered before it. If the reaction is negative, vaccination can be performed immediately after the test.

If the baby was given some kind of prophylactic vaccination, the test is allowed no earlier than a month after vaccination.

Reviews

You can read mostly positive reviews about the use of Diaskintest in childhood, because thanks to this medicine, you can determine whether a child is sick with tuberculosis.