Allergy diagnostics include specialized skin testing, nasal testing, direct and indirect allergy testing, measurements, oral, nasal, and throat testing, and laboratory testing. Skin tests
- Prick test – a drop of an allergen extract is applied to the patient’s skin and then a lancet is used to prick the skin about 1 mm; the result is then read after about 15 minutes. A positive reaction appears as a bright wheal (edema) with a reddened area (erythema). A test reaction is considered positive (+) from a wheal diameter ≥ 3 mm.
- Prick-to-prick test – first pricked with the lancet into the suspected allergen source, then with this lancet into the skin of the patient.
- Scratch test – here, allergen extracts are also applied to the patient’s skin, which is then scratched superficially for a few millimeters with a lancet
- Rub test – the presumed allergen is rubbed on the inside of the forearm; if positive failure shows after a few minutes an erythema (areal skin redness) or wheals
- Epicutaneous test (synonyms: patch test, patch test, patch test) – in this test, a patch is applied to the patient’s skin containing various allergens.Reading times:
- Tag 0: stick epicutaneous patch.
- Day 2 (48 hours): remove patch, first reading.
- Day 3 (72 h): second reading.
- Day 7 (168 hours): third reading
Notice:
- If the aim is to achieve the highest possible specificity (probability that actually healthy people who do not suffer from the disease in question are also detected as healthy in the test), an exposure period of two days is recommended.
- If it is a matter of high sensitivity (percentage of diseased patients in whom the disease is detected by the use of the procedure, ie, a positive finding occurs), can be considered to limit the exposure duration to one day.
- To differentiate a true allergic reaction from increased skin irritation, the detergent sodium lauryl sulfate is co-tested as an irritant control.
- Medications that should be discontinued before performing the epicutaneous test:
- Discontinue steroid one week before epicutaneous test.
- Antihistamines: discontinue at the interval of 5 half-lives.
- Intracutaneous test – similar to the prick test, but more sensitive! In this test, a defined amount of an allergen extract is injected intracutaneously (i.e. injection of the allergen into the dermis / dermis) and also read after 20 minutes against a blank test.Caveat (Warning)! There is a risk of a high-grade allergic reaction with this test. [Ready allergen solutions for intradermal testing are probably no longer available in Germany].
Note: A positive test reaction only detects allergic sensitization. The clinical relevance can not be assessed by a skin test (HT). This is only possible in conjunction with a detailed medical history or in doubtful cases with nasal/conjunctival provocation. Serologic tests
- Radio-Allergo-Sorbent Test (RAST) – measurement of allergen-specific IgE antibodies in serum; these are responsible for mediating certain allergic reactions.
- Enzyme-linked immuno sorbent assay (ELISA) – method for detecting IgE antibodies in serum.
- CAP fluorescent enzyme immunoassay (CAP-FEIA) – method for the detection of IgE antibodies in serum.
- Eosiniphilic cationic protein (ECP) – this substance is formed by eosinophils – cells of the immune defense – and can be used as a progression parameter in allergies.
- Tryptase – an enzyme which is secreted by mast cells – important cells in allergic reactions – and thus can be considered as a parameter in the diagnosis of allergy.
Provocation tests
- Nasal provocation test – in which an allergen extract is sprayed into the nose; subsequently, the reaction can be detected using rhinomanometry – measurement of the pressure difference between the nasal inlet and nasopharynx during inhalation and exhalation.
- Bronchial provocation test – here the allergen extract is inhaled and then the reaction is measured by pulmonary function testing
- Oral provocation test – elimination of the food that triggers symptoms, with exposure over 2-3 weeks to observe the onset of symptoms.
Provocation tests can cause severe reactions, so such tests should only be performed by physicians experienced in allergology, who can also perform appropriate emergency measures. Dietary tests
- Elimination diet – avoidance of suspected foods.
- Search diet – low-allergen basic diet that leads to freedom from symptoms, followed by a gradual search diet.
Allergy diagnostics is combined with allergy counseling.
Your benefit
Allergy diagnostics detects your allergy triggering substances. Previously unclear reactions of your skin, ear, nose, throat, eyes and ears, digestive system and lungs are detected and can be directed to the right therapy.Allergy diagnostics is used to detect and analyze an allergic disease and the substances that trigger it.
