Cast

Synonym(s)

cellular antigen stimulation test

Cellular antigen stimulation test. In vitro methods of allergy diagnostics.

In the case of undetectable allergy-specific antibodies in serum or plasma, CAST can be used to test the current sensitivity of living granulocytes to foods, food additives and drugs.
This method is the method of choice especially for diagnostic questions where provocation tests are difficult to perform, e.g. under continuous therapy with antihistamines, in atopic eczema and in children under 6 years of age.
The method is also of great value in the diagnostic detection of intolerance reactions (pseudoallergies), i.e. non-IgE-mediated allergic reactions. Typical examples are analgesic-induced drug intolerances (e.g. when taking aspirin) and a number of food and drug additives. These intolerance reactions originate in particular from eosinophilic granulocytes, which are also tested at CAST.

Leukocytes are isolated from the patient blood sample and incubated successively with interleukin-3 and the desired allergen or allergen mixture. After allergen stimulation, mainly basophilic granulocytes synthesize de novo allergic inflammation mediators, especially sulfoleukotrienes such as LTC4 and its metabolites LTD4 and LTE4.
These inflammatory mediators, whose synthesis and release are both IgE-mediated and non-IgE-mediated in intolerance reactions, can be measured in the cell supernatant by ELISA. In this method the sum of the sulfoleukotrienes released from all leukocytes is determined.

Fischer TW et al (1999) Non-immunologic contact urticaria from chrysanthemum confirmed by the CAST method. Complement-activated (C5a) cellular antigen stimulation test. Contact dermatitis 41: 293-295
Star A (2001) Cellular antigen stimulation test (CAST). A new possibility in diagnosis of aspirin-sensitivity rhinosinusitis? HNO 49: 161-163