Allergy testing: indications and norms

Allergy testing is a necessary study that helps to identify the antigen that provokes an allergic reaction and begin timely treatment. Moreover, it is almost impossible to achieve a result and really stop an allergy if you do not find out the etiology of the disease and the allergen itself. The diagnostic method involves taking skin tests "in vivo", as well as the "in vitro" method, which studies blood antibodies. These are allergy tests and the detection of immunoglobulin IgE in the blood, the main substance responsible for the aggressive reaction of the immune system to an allergic antigen.

Allergy tests are prescribed mainly for hay fever, as well as for atopic dermatitis, drug allergies, food allergies, rhinitis and sinusitis of allergic etiology, and less often for bronchial asthma and pneumonia. It is not recommended to conduct allergy tests in cases of severe infectious diseases, tuberculosis, exacerbations of allergies, in cases of hormonal therapy, and allergy tests are not performed on pregnant women or in the general serious condition of the patient.

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Dermal (skin tests)

Dermal (skin tests) are conventionally divided into direct and indirect. Direct skin tests involve the introduction of an antigen (allergen) under the skin or on the skin, an indirect method is the introduction of serum containing IgE, and then the introduction of the antigen. Technically, tests also have options - they are done by drip, scarification, application or injection (prick test). The method directly depends on the form of the allergic disease, the degree of sensitivity of the suspected reaction. All this information is provided by the previously collected anamnesis. Allergy analysis in the form of an allergy test is based on a possible response to the introduction of the suspected allergen. Depending on the reaction - immediate or delayed, the result can be detected within 30 minutes or 8 hours. After 20-30 minutes, an immediate reaction is determined by the area of hyperemia at the site of the test, as well as by the blister. If tests are conducted for household or food allergens, then information must be waited for up to eight hours, and sometimes even a day. Allergy tests are examined under fairly bright lighting, a positive test is considered if the papule reaches 2 mm.

One procedure may include up to 20 tests for different allergens. In order for the allergy test results not to be distorted, the patient must exclude the use of antihistamines.

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Allergy test using IgE immunoglobulin determination

An antibody called IgE is responsible for all allergic reactions. Immunoglobulin IgE functions in the blood serum for no more than three days, about two weeks in the membranes of basophils and mast cells. This antibody has the property of fixing on the cells of the mucous membrane, on the skin, so blood is not its favorite place of dislocation. Any increase in the level of IgE in the plasma may indicate one or another form of allergic reaction. The immunogram in children is more informative than in adults. However, this method of analytical research in allergies is quite effective and is actively used throughout the world. The test is also good because a person does not need to directly contact the allergen, as in the case of allergy tests. In addition, the test has no contraindications, it is suitable even for severe, acute forms of allergic disease.

Indications for which IgE analysis is performed:

• All forms and types of allergies;
• Assessment of the risk of developing allergies in case of a family history;
• Helminth infestation.

Allergy testing using IgE antibody detection requires adherence to certain rules, including the following:

• Elimination of any physical activity and emotional stress;
• The procedure is performed on an empty stomach;
• On the eve of the procedure, during the day it is advisable to follow a gentle diet, exclude alcoholic drinks, strong coffee and tea.

IgE norms depend on age and should correspond to the following indicators:

• Children under 1 year – 0-15 units/ml;
• Children from 1 year to 6 years – 0-60 units/ml;
• Children from 6 to 10 years old – 0-90 units/ml;
• Children from 10 to 16 years old – 0-200 units/ml;
• Adults – 0-200 units/ml.

Any increase in the normal range indicates an active response of immunoglobulin IgE to the invasion of an antigen or infection.

The analysis shows the reaction of immunoglobulin to almost all food antigens, there are about 90 names in the list. The result is the following indicator options:

• Negative - up to 50 units/ml;
• Low sensitivity + 50-100 units/ml;
• Moderate sensitivity ++ 100-200 units/ml;
• High sensitivity +++ more than 200 units/ml.

Allergy testing - skin tests or immunological research, both methods are necessary and important in order to identify the allergen in time and determine therapeutic actions, prescriptions, the analysis is also used as a test of the body's reaction to the use of various types of medications to determine their effectiveness.

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