Prik-test (from the English. Prick - "injection") - one of the skin allergy tests used in the diagnosis of allergic diseases.
To skin allergological tests include skid-test (previously, instead of them did scarification), intradermal and application. Prik-test is a fast, convenient, inexpensive and reliable method of allergy diagnosis of IgE-mediated allergic diseases. Class E specific immunoglobulins (specific IgE, sIgE) are produced by the immune system in hypersensitive people under the influence of various allergens .
Prik-test is used to diagnose immediate-type allergic reactions (differently - IgE-related, or reagin, or type 1 hypersensitivity reactions, according to the classification of Gell & Coombs, 1977).
Testing is carried out with solutions of various allergens : pollen (trees, grasses), epidermal (cats, dogs, etc.), household ( house dust mites (D. pteronyssinus, D. farinae), mold (Cladosporium, Alternaria, etc.), medicinal , production and others.
Prik-test allows you to confirm only allergic reactions of one type - IgE-conditioned, but not informative other, non-IgE-conditioned.
However, the presence of a positive test result may not be evidence of the disease (like any test, it can be false-positive, as well as false-negative). To diagnose an IgE-mediated allergic disease, the doctor must compare the test results with other patient data (history of the disease, objective symptoms, data from other examinations), and also exclude other causes that can cause the same symptoms.
Prik-test has no age restrictions. However, skin reactivity may vary with age.
Content
Primary Test Method
The skin of the forearm is treated with ethanol . At a distance of 2-3 cm, drops of solutions are applied: a) histamine (positive control), b) 0.9% sodium chloride (negative control), c) allergens. A drop of the solution is used to prick the skin with a special nail, the needle length of which is 1 mm (which allows the test to be painless and bloodless; the presence of blood at the skin puncture site with a lace can lead to a false result). For one priick (injection), one sterile prik-lancet is used, after which it is considered used and is to be disposed of. Medical personnel may sign on the injection site which solution was applied. The test is evaluated in 10-15 minutes.
A positive answer in the prick test is the presence of a blister of 3 mm or more. Counting is performed on the largest blister diameter.
When a positive reaction to a solution of histamine and negative for a solution of sodium chloride evaluate the reaction to solutions of allergens . If the response to a positive control is negative, the test is false negative. If the reaction to a negative control is positive, the test is false positive.
Factors Affecting Test Result
- correct technique
- drugs that suppress the skin reaction ( antihistamines , hormones , antidepressants)
- age (in children and the elderly less pronounced reaction)
- standardization of the allergen solution
- dermographism
Sources
See also
- Allergic Skin Testing
- Allergic Testing
- Allergy Diagnostics