Allergy diagnostic tests

Description:

Allergy diagnostic tests — a highly specific and sensitive diagnostic method of allergic and infectious diseases in which pathogeny the allergic component prevails. Tests are based on local or general reaction of a sensibilized organism in response to administration of offending allergen.

Purpose of allergological skin tests:

Allergy diagnostic tests have special value at diagnosis of allergic diseases as definition of allergen or group of the allergens which caused hypersensitivity disease allows to apply further these allergens to organism desensitization — the most specific and perspective method of treatment of allergic diseases.
At diagnosis of allergic diseases in the course of collecting the anamnesis allocate alleged group of allergens which could cause hypersensitivity disease in the patient. With these allergens carry out allergy diagnostic tests out of a phase of an exacerbation of a disease. In parallel with administration of allergens enter control solutions — solvent of allergens and normal saline solution.

Classification of allergological skin tests:

I. Skin tests:
1) qualitative:
— straight lines
— intradermal
— scarifying
— prick
— application
— drop
— indirect (Prausnittsa-Kyustner's reaction)
2) quantitative (allergometrichesky titration)
II. Provocative tests:
— conjunctival
— nasal
— inhalation
— cold
— thermal
— exposition
— eliminative
— leykotsitopenichesky
— thrombocytopenic.

Conducting allergological skin tests:

Apply skin and provocative allergy diagnostic tests.
Skin tests — the safest and simple type of allergy diagnostic tests. Depending on a way of administration of allergen apply application, scarifying and intracutaneous tests.
Application tests apply at hypersensitivity to simple chemicals (benzene, gasoline, etc.), to some medicines (iodine, novocaine, etc.) at patients with contact dermatitis.
On the unimpaired site of skin of a forearm, back or stomach impose the piece of a gauze  moistened with allergen solution (in the concentration which is not causing irritation of skin in healthy people), and stick with an adhesive plaster for 20 minutes. The result is estimated in 20 minutes, 12 and 24 hours from the moment of putting allergen. Emergence on skin in the place of contact with allergen of a hyperemia and hypostasis demonstrates existence of hypersensitivity to this allergen.
Scarifying tests apply at hypersensitivity to pollen, household and epidermal allergens at patients with pollinoses, bronchial asthma, allergic rhinitis, small tortoiseshell and a Quincke's edema. Apply drops of allergen and control solutions on skin of the palmar side of a forearm. Carry out by the scarificator, separate for each allergen, through each drop parallel scratches. In 20 minutes and 24 hours make assessment of tests. Edematization in a zone of scarification demonstrates positive reaction.
Intracutaneous tests apply at hypersensitivity to bacterial and fungal allergens at patients with bronchial asthma, chronic recurrent small tortoiseshell and infectious diseases. These tests by 100 times are more sensitive, than scarifying, but are less specific and give more complications.
The Tuberkulinovy syringe vnutrikozhno enter from 0,01 to 0,1 ml of solution of allergen. At development of an urtikarny blister in 15 — 20 minutes after introduction — reaction positive immediate type. Emergence in the place of an injection of a zone of a hyperemia with infiltrate in 24 — 48 hours demonstrates positive reaction of the slowed-down type.
Some allergens (penicillin and other antibiotics) at statement of test at patients with hypersensitivity to them can give heavy complications (shock) when carrying out scarifying and especially intracutaneous tests. To these allergens it is better to apply reaction of passive transfer of hypersensitivity on Prausnittsa to definition of sensitivity — to Kyustner. At the patient with an allergy to antibiotics receive blood serum, antibody-containing. Passively sensibilize the site of skin of the healthy person, entering it vnutrikozhno the patient's serum. In 24 hours enter allergen into an injection site of serum. Reddening of this site of skin of the healthy person demonstrates existence at the patient of the antibodies specific to the studied allergen.
With hypersensitivity of the slowed-down type reaction of passive transfer is carried out with a suspension of lymphocytes of the patient.
Provocative tests apply in cases when data of the allergological anamnesis do not correspond to results of skin tests. Provocative tests are most specific in diagnosis of allergic diseases. Apply nasal, conjunctival, inhalation and other provocative    tests.
The nasal test is applied at diagnosis of allergic rhinitis. A pipette dig in in both half of a nose on 2 — 3 drops of control liquid. In the absence of reaction begin a research with the increasing concentration of allergen. At difficulty of nasal breath, sneezing, a rhinorrhea test is considered positive.
The conjunctival test is applied at diagnosis of pollinoses with the conjunctivitis phenomena. After preliminary testing with control solution allergen is dug in a pipette in the lower conjunctival sac. Reddening, dacryagogue and an itch a century — signs of positive reaction.
The inhalation test is applied at diagnosis of bronchial asthma. Solution of allergen is given to the patient by means of the aerosol sprayer. At positive test the vital capacity of lungs decreases by 10%, the bronchospasm which is stopped bronchial spasmolytics develops. At use of provocative tests consider as well late reactions.
Cold test is applied at diagnosis of a chronic recurrent small tortoiseshell. The piece of ice is fixed on forearm skin for 3 minutes by means of bandage. At a positive take in 10 minutes after removal of ice on skin the urtikarny blister is formed.
Thermal test is applied at diagnosis of a small tortoiseshell. The test tube with hot water (t ° 40 — 42 °) is placed for 10 minutes on skin of a palmar surface of a forearm. Positive reaction is characterized by formation on site of contact of an urtikarny blister.
Allergy diagnostic tests apply also at diagnosis of some infectious and the parasitic diseases which are followed by an allergic sensitization of an organism. At diagnosis of tuberculosis apply a scarifying Pirquet's test and an intracutaneous test to Mant. As allergen apply cultivations of the dry purified tuberculine. At diagnosis of a brucellosis apply  an intracutaneous test of Byurne. As allergen serves the brucellin solution containing an antigenic set of three various causative agents of a brucellosis. At diagnosis of an echinococcosis apply Kasoni intracutaneous test. As allergen serves the extract from echinococcus bubble contents. At diagnosis of a tularemia apply an intracutaneous test with tularin — the suspension of bacteria killed with heating. At diagnosis of dysentery apply test with dizenteriny Tsuverkalova.