In clinical practice, a large number of methods for diagnosing food intolerance and food allergy are used, which can be grouped as follows:.

- anamnestic;

- physical;

- elimination and provocative tests;

– scarification skin tests with food allergens;

- cell tests with food allergens (basophilic Shelley test, phagocytic activity of blood);

– serological studies (qualitative and quantitative analysis of total and specific IgE, IgG).

True food allergy can be both the cause of acute or chronic diseases, and the pathogenetic consequence of a wide variety of pathological processes..

A comprehensive general clinical examination of a patient with suspected or already verified food allergy must be combined with food allergy detection tests..

Each of the methods for diagnosing food intolerance considered below is not universal, providing a solution to a certain range of clinical problems..

It is advisable to use combinations of diagnostic tests in accordance with the diagnostic search algorithm individual for each patient..

Any methods have limits to their diagnostic capabilities, expressed in terms of sensitivity, specificity and reproducibility of the method..

The sensitivity of a diagnostic method is understood as its ability to recognize a disease (pathological condition), in cases where it exists..

The sensitivity of the diagnostic method characterizes the proportion (in percentage terms) of correctly diagnosed diagnoses out of the total number of patients with a verified diagnosis of the type in question..

Sensitivity (%) \\u003d ((Number of actual patients confirmed by this method) / (Total number of actual patients from all examined)) x 100 The specificity of a diagnostic method is understood as its ability to give a negative result in the absence of a disease (pathological condition). The specificity of the diagnostic method characterizes the property of this method (method) to correctly identify persons (in percentage terms) who do not have this disease, among those to whom this method (method) is applied.

Specificity (%) \\u003d ((Number of healthy individuals identified by this method as healthy) / (Number of really healthy people from all examined)) x 100 The reproducibility of a diagnostic method is a statistical test for assessing its stability by analyzing the frequency of deviations (in percentage terms) between indicators.

Reproducibility (%) \\u003d ((Number of matching positive assessments (indications)) / (Total number of positive assessments (indications))) x 100 The closer the calculated sensitivity, specificity and reproducibility of a new research method to 100%, the higher its diagnostic capabilities,.

Choosing and using a diagnostic method.

The choice and use of new research methods optimal for solving specific diagnostic problems should be carried out taking into account indicators of their sensitivity, specificity and reproducibility..

Anamnestic method of diagnosis.

The anamnestic method for diagnosing food intolerance is a very important and mandatory initial stage of a diagnostic search.. Attention should be paid to the frequency of occurrence of clinical episodes of the pathological reaction of the body and their relationship with the use of food, the detail of symptoms resembling food allergies, as well as the time relationship between food and the onset of clinical manifestations..

Physical diagnostic method.

The physical diagnostic method involves a generally accepted objective examination of a patient with developed symptoms of the disease.. When diagnosing food intolerance, it is advisable to pay special attention to the condition of the skin, visible mucous membranes, conjunctiva of the eyes, sclera, examine the nasal cavity, mouth, note possible pathological phenomena, especially wheezing, during auscultation of the lungs..

Elimination and challenge tests.

Elimination and provocative tests are usually used in the absence of the ability to conduct modern serological methods of research.. They are screening and reveal an inadequate response of the body to certain foods..

Elimination studies are indicative diagnostic methods and only allow to suspect intolerance to a particular food product in patients.

The principle of compiling therapeutic diets is to exclude the most common food allergens.. Initially, 4 basic diets were proposed: with the exception of milk and dairy products, with the exception of cereals, with the exception of eggs, and with the exception of all three listed food components..

The exemption must be total, not even minimum quantities of the relevant products are allowed.. The patient is prescribed one of the diets for a period of 1-2 weeks and fix the effect of elimination; in his absence, the diet is changed.

If the use of elimination diets does not reach the goal, diagnostic fasting is recommended for a period of 3-4 days, during which the patient is only allowed to drink mineral or plain water.. If a complete or partial remission occurs during the fasting period, it can be assumed that the disease is associated with food..

After starvation, products are gradually included in the diet (one at a time within 4 days) with constant registration of subjective and objective manifestations of the disease. Subsequently, the foods that caused the exacerbation are excluded from the diet..

This inclusion of products is a provocative test. At first glance, it seems that the described procedures with diets, diagnostic fasting and provocative testing with food products are logical and uncomplicated in terms of technique..

Unfortunately, in practice, the doctor in the process of research faces difficulties in interpreting the results.. The fact is that the study obviously assumes only one variant of causal dependence: food - symptoms of the disease.

In fact, skin, gastrointestinal and especially respiratory syndromes can change their intensity, disappear and recur again depending on many exogenous and endogenous influences, both allergenic and nonspecific (weather changes, ambient temperature, strong odors, psychogenic stimuli).

Linking clinical dynamics to nutrition is always problematic. In addition, an open study, especially with a subjective nature of the interpretation of the results, is always fraught with suggestion..

To avoid the psychogenic influences of the doctor on the patient and the patient on the doctor, there is a technique for conducting provocative tests with food products "

The methodology boils down to the following. The test products are dried and used in the form of powders.; 8 g of powder corresponds to approximately 100 g of food. Powders in the amount of 200-500 mg are placed in opaque capsules. 2 weeks before the study, the corresponding products are excluded from the diet.

As a placebo, exactly the same glucose capsules are prepared. Capsules are given to the patient on an empty stomach in such a way that neither the patient nor the examiner knows what is contained in the capsules.. A third party knows this and subsequently analyzes the received data. The initial dose, depending on the severity of clinical manifestations, ranges from 200 to 2000 mg (in several capsules).

Symptoms often appear within a few minutes to 2 hours, but sometimes later. If symptoms do not appear after 24 hours, the study is repeated, increasing the dose by 2-10 times, up to a maximum of 8000 mg.. If the last dose is well tolerated, then it is considered that there is no intolerance to the corresponding product..

If placebo reactions occur, suggest a neurogenic reaction or coincidence with another non-nutritive causative factor. In patients with food shock reactions, provocative tests are dangerous and are not recommended..

Elimination and provocative tests are easy to perform, available to physicians even in primary care. However, they are characterized by large diagnostic errors..

According to our research, the combined use of elimination diagnostic diets and provocative tests has a sensitivity of about 68%, and a specificity of 51%..

We can reasonably conclude that elimination and provocation tests should be used in clinical practice in exceptional cases: in the absence of modern methods for the qualitative and quantitative assessment of diagnostic data.

Scarification skin tests.

Skin scarification tests with food allergens are traditional immunological tests that help confirm suspected food allergies and identify a specific food allergen..

The test procedure is simple: on the skin of the anterior surface of the forearm, linear or dotted superficial incisions are applied with a scarifier, on top of which a liquid extract of a specific food product is fixed..

The test is assessed as positive if itchy redness occurs in the scarification area.. Unfortunately, the diagnostic significance of this method is not high enough: sensitivity - no more than 65%, specificity - about 50% [Roit A.. and etc. , 2000].

Practice has shown that patients do not give a skin allergic reaction to a known food allergen, while many patients with false positive reactions during scarification allergological tests.

Cell tests.

Cellular tests with food allergens (basophilic Shelley test, leukocytopenic and thrombocytopenic provocative tests, etc.). ) many authors used in the clinic solely to improve the diagnostic capabilities of other studies, primarily such as elimination and provocative tests.

The diagnostic information content of these research methods is relatively small, therefore, at present, they have only historical significance.. It should be noted the method of diagnosing food intolerance, called by the authors " by: Semenova N. , Medvedev S. , Reshetova N. Medical Department. — 2002. - No. 4. - FROM. 16-17).

" Orekhovich RAMS, and, according to the authors, allows you to identify the hypersensitivity of the body, which may be based on various mechanisms of allergic and pseudo-allergic nature. The rationale for the method is as follows.

At the final stage of food intolerance of various types, the release of histamine is observed not only by mast cells of the mucous membranes of the gastrointestinal tract, but also by many cellular elements of the blood, especially phagocytes.. Histamine "

The impact on the phagocytic cell of a nonspecific stimulus leads to the launch of a respiratory flash, which is accompanied by the generation of reactive oxygen species and, accordingly, a flash of chemiluminescence (CL). The detection of this effect by assessing whole blood CL in the presence of a food allergen was taken by the authors as the basis for diagnosing this pathology..

Clinical studies of the diagnostic significance of "

It can be concluded that the method of diagnosing food allergy "

Serological studies.

Serological tests are now increasingly used to diagnose both true food allergy associated with IgE-dependent mechanisms of immediate hypersensitivity, and to identify IgE-independent forms of food allergy, that is, delayed allergy.. Conduct a qualitative and quantitative analysis of total and specific IgE and IgG of blood serum.

Among the proposals for the diagnosis of IgG-mediated food intolerance, there have long been numerous more or less modern tests produced under different names.. All of them are based on the method of determining " The authors consider intolerance a type II hypersensitivity reaction (cytotoxic reaction) and try to identify the antigen-antibody+-leukocyte complexes under a microscope..

It is obvious that such an interpretation of the results is largely empirical and in any case depends on the diagnostician.. In addition, from a pathophysiological point of view, a strong covalent bond of the antigen with any tissue is required for the manifestation of a cytotoxic effect..

It takes time to metabolize the antigen; such processes do not occur in the blood.. Moreover, during cytotoxic reactions, not neutrophils, but cytotoxic lymphocytes (T-killers) and macrophages are included in the complex..

The possibility of using morphological changes in leukocytes as an indirect indication of the cytotoxicity of a food product for other cell populations (tissue target cells) has not been confirmed..

In a number of immunological methods for assessing nonspecific parameters of the immune status in most atopic diseases, which include true food allergy, the determination of the amount of total IgE is of the greatest importance..

There are various methods for quantifying total IgE. The most commonly used enzyme-linked immunosorbent assay (ELISA).

For the screening determination of food IgG in most countries of the world, the most widely used method is ELISA (enzyme linked immunosorbent assay - enzyme immunosorbent assay), which determines circulating antibodies that recognize purified food antigens and are fixed to them..

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