Skin allergy test

Allergy tests are used to detect allergies to allergens tested, where the investigated person or the examined animal is suffering. The following different processes are advantageously applied:

• 2.1 prick
• 2.2 intracutaneous
• 2.3 rub test
• 2.4 patch test
• 2.5 ROAT
• 2.6 atopy patch test

• 3.1 Nasal provocation testing
• 3.2.2 bronchospasmolysis

• 4.1 Non-specific inhalation provocation
• 4.2 Specific inhalation provocation

In vitro test method

Determination of antibodies

In blood samples so-called free IgE antibodies can be measured. On the one hand the total IgE levels can be measured, which encompasses all free IgE antibodies. This value allows a statement as to whether generally increased IgE antibodies are formed. Increased total IgE levels are not only in allergic diseases before, but also in parasites and certain hematological diseases. On the other, allergen-specific IgE antibodies can be demonstrated. This case, therefore, the IgE levels are determined, which are directed specifically against an allergen source. Common today are using FEIA (fluorescence enzyme immunoassay) and EIA ( enzyme immunoassay) regulations, the highlighted instead of the previously used radioactive ( 125I ) reagents, enzyme-labeled reagents. Here goes for the healthy man is a reference range of <100 kU / L for total IgE. Measurements for allergen - specific IgE are considered negative for values ​​< 0.35 kUA / L. Class 1 ( 0.35-0.70 kUA / L ) is considered borderline positive. Positive classes are 2-6 ( Class 2: 0.70 to 3.5 kUA / L; class 3: 3.5 to 17.5 kUA / L, Class 4: 17.5 to 50 kUA / L; class 5: 50-100 kUA / L; class 6 > 100 kUA / L). Rather outdated measurement methods are RIST (radio - immuno- sorbent assay) for total IgE and RAST (Radio - Allergo - sorbent assay) for allergen - specific IgE. Quantitative measurement of IgE antibodies in the blood correlates only poorly with the clinical picture. That is, the measurement of IgE antibodies in the blood provides an indication of the sensitization of an allergic, but only a limited assessment of the severity of symptoms and no statement about the nature of the symptoms. It may also be that allergen - specific IgE antibodies in spite of awareness can not be detected.

Meanwhile, there are some vendors on the market that not only identify the source of allergens, but also many of the relevant for sensitizing allergen components (eg ImmunoCAP / ISAC ). In these tests, not the antibodies against the allergens measured but individual proteins of the allergens are analyzed, the test is more informative than the above test methods. In the more innovative ISAC ( Immuno Solid phase Allergen Chip) is a microchip - panel test with more than 100 allergen components ( aero-and food allergens, insect venom allergens, molds, latex). Such allergy screening is currently not provided by statutory health insurance, as opposed to the ImmunoCAP. The advantage of this composite study is that with relatively little use of an extremely wide range of blood can be tested to allergens. This is advantageous especially for small children and a complicated history. However, there are also allergens and allergen components examines the history of have no influence on the clinical picture.

Determination of inflammatory markers

Histamine

• Histamine ( 2 - (4 -imidazolyl ) ethylamine ) is a natural product that acts as a tissue hormone and neurotransmitter in the human or animal organism, and is also widely distributed in the plant kingdom and in bacteria. In humans and other mammals, histamine plays a central role in allergic reactions and the immune system, that is, in the defense against foreign substances involved. Also in the gastrointestinal tract in the regulation of gastric acid secretion and motility as well as in the central nervous system in controlling the sleep -wake cycle and appetite control histamine acts as an important regulator. Biochemically it is a biogenic amine, which is formed from the amino acid histidine, and in particular, mast cells, basophils and neurons is stored.

→ Main article: Histamine

Tryptase

Leukotrienes

• Leukotrienes were detected in leukocytes ( white blood cells) and are chemically derived from arachidonic acid ( a polyunsaturated fatty acid four ) derived. You even have three double bonds and belong to the group of eicosanoids. Your role in metabolism is related to allergic or inflammatory reactions of the body (eg, asthma ).

→ Main article: Leukotriene

Eosinophilic cationic protein (ECP )

• The eosinophil cationic protein ( eosinophil cationic protein german, ECP) is selectively synthesized in eosinophilic granulocytes. It is next to EDN one of the main components of the eosinophien granules. Both proteins are ribonucleases of the RNase superfamily A. The eosinophil granulocytes play an important role in the pathogenesis of bronchial asthma. There is a close correlation between the number of eosinophils and the concentration of ECP. Since a correlation between the ECP concentration in the blood and the degree of asthma severity is, this parameter can contribute to the progress of a asthma therapy, for example.

→ Main article: Eosinophilic cationic protein

Cellular tests

The lymphocyte transformation test (LTT ) is a laboratory method for the detection of antigen-specific T lymphocytes. It finds its application in immune function diagnostic medicine. For a few years he will (IV ) (eg, drug allergy, metal allergy) and in the pathogen diagnostics (eg disease diagnostic ) used in allergology for detecting certain allergic reaction of the delayed type.

Several university hospitals and specialized institutes have standardized the process. For drug allergy test, 2006, the recommendations of the German Society of Immunology and Allergology ( DGAI ) was added. For other allergy issues, however, the clinical significance of demonstrated sensitization is still controversial. Therefore, the LTT should only be used in addition to the patch test and then with allergy issues, if this is not feasible.

→ Main article: lymphocyte transformation test

Skin tests

Prick test

The prick test (english: = prick puncture ) is used to detect a so-called type I allergy, such as a sensitization to pollen or animal hair. A defined allergen extract is dropped onto the skin and this is then easily pierced with a lancet so that the particular substance can penetrate into the epidermis. The test reaction can be read ( with histamine and drug- free negative control positive control) after 20 minutes compared to two always mitdurchgeführten empty tests. Are assessed on the skin redness and Quaddelgröße. The prick test is usually painless.

A lower mold of the prick test is the so-called prick to prick test, in which, for example, food products can be tested using the food, and then the skin is pierced at first.

Intracutaneous

Here, a defined amount of allergen extract (eg, insecticides or food extracts ) is injected intracutaneously and also after 20 minutes against a blank test (see above) read. However, there is the risk of a severe allergic reaction. It is also used for the detection of type I allergy.

Rub test

Allergy test, which is also suitable for the detection of type I allergies, in which the skin is first scratched the surface, and then the tested allergen ( for example animal dander or foods ) is rubbed natively. Test reading is also performed after 20 minutes.

Patch test

This test is used to detect a so-called type IV allergy, such as to nickel salts ( nickel sulfate) or fragrances. This defined preparations of allergens to be stuck in carrier substances ( such as petroleum jelly or water) on the skin under test chambers. The test reading should be done every 24, 48 and 72 hours (in exceptional cases even longer). Here, it is also evaluated the response curve ( rising or falling response ) versus time.

ROAT

The repeated open application test is used to clarify an unclear or ambiguous reaction in the patch test. To assess the clinical relevance of the allergen in question is applied twice daily for one week in a limited area on the inside of the upper arm.

Atopy patch test

This special form of the patch test is used to identify type I allergens ( inhalant allergens ) as a trigger of atopic eczema. As a carrier substance is used Vaseline. The test area should be free of symptoms at start of test. As a positive test reaction occurs a disturbance of the barrier function of the skin, which leads to a dermatitis.

Provocation tests

Nasal provocation testing

The allergic rhinoconjunctivitis ( allergic rhinitis, hay fever) is one of the most common allergic diseases. It often begins in childhood, often leads to troublesome symptoms for decades and has an impact on the social life, school performance and labor productivity of patients. It is clinically defined as a symptomatic hypersensitivity reaction of the nose induced by an IgE-mediated inflammation of the nasal mucosa as a result of allergen exposure.

A positive result of mastzellgebundenem allergen- specific IgE in skin test or specific IgE in serum is an immune response to an allergen, however, is not synonymous with evidence of allergic disease. The aim of the nasal provocation tests with allergens is associated with clinically current sensitization ( allergy) to separate patients against inhalant allergens of such patients, although sensitization, but under natural exposure conditions, no symptoms have ( clinically silent sensitization), is of diagnostic importance, particularly in of rhinitis.

The nasal provocation test (NPT ) reproduces the response of the nasal mucosa to an inhaled substance from the environment under controlled conditions. It brought the suspected allergen to the nasal mucosa and documented the resulting clinical emergency response. The change in nasal patency after allergen air application is active anterior rhinomanometry measured by, sneezing, secretion and remote symptoms are detected by means of a score.

Pulmonary function tests

The peak flow is a measure that indicates the speed at which a person can blow air out of their lungs. This is measured with a peak flow meter or a spirometer. In healthy people, the peak flow value is approximately between 400 and 700 l / min. In those with respiratory problems such as asthma, the value is lower. In asthma airways are narrowed and thus the blow-off amount per minute is substantially reduced. For this reason, the peak flow is considered to be so important in patients with respiratory disease, such as the daily measuring of blood pressure in patients with hypertension.

Bronchospasmolysis

When bronchospasmolysis the reversibility of bronchial obstruction is tested. For this purpose, it is examined whether the patient by use of a β2 - sympathomimetic ( for example: terbutaline, fenoterol or salbutamol ) can achieve a reduction in the airway resistance. This goes hand in hand with an increase in volume in one second (FEV1). Typically, the obstruction in the course of bronchial asthma is reversible, the obstruction in chronic obstructive bronchitis is never completely reversible.

Inhalation provocation

Non-specific inhalation provocation

Under non-specific inhalation provocation refers to studies with bronchokonstriktorisch effective pharmacological substances. The investigation is indicated in patients with chronic cough and / or shortness of breath of unknown cause, if there is no measurable spontaneous obstruction. Of methacholine To carry out today mainly used with the cholinergic methacholine. Compared to other substances such as histamine or carbachol is not expected to experience adverse local or systemic side or late effects.

→ Main article: methacholine

Specific inhalation provocation

Specific inhalation provocations serve to prove a particular allergen as a trigger of allergic bronchial asthma. Possible indications are also in the field of occupational health reports ( for example baker's asthma ) or the definitive proof of the causal allergen, such as when serious therapeutic measures parental or social consequences ( career change ) result. As a further indication for specific provocations are insect bites, where you can check the success of therapy at a hyposensitization with insect venom allergies in individual cases.

Provocations with food and additives