Basophil activation test

The basophil activation test (BAT) is a method for diagnosing allergies of the immediate type (type I) or pseudo-allergic reactions. It uses an in vitro method to represent the in vivo reaction to allergen exposure. It is therefore an important allergological diagnostic component for immediate reactions and closes a diagnostic gap in unclear or difficult cases where there are discrepancies between the medical history and in vivo/vitro diagnostics, or where serological IgE diagnostics are not available (Strohmmeier D et al. 2017). Furthermore, it is an alternative test for patients in whom skin testing is not possible for various reasons (e.g. in cases of high sensitization with the risk of shock fragments during testing). However, the test is not suitable for detecting delayed-type hypersensitivity reactions (type IV reactions).

Particularly in the diagnosis of IgE-mediated immediate type reactions to various allergens including drugs and insect venoms. In the clarification of penicillin allergy, the use of CD63 or CD203c (see CD classification below) and the determination of specific IgE can increase sensitivity. The significance of BAT in non-IgE-mediated reactions, e.g. to non-steroidal anti-inflammatory drugs, has not yet been conclusively clarified.

In summary, the use of BAT should be considered above all (Glässner A et al. 2024):

• If it is known that the allergen leads to false positive results in skin tests.
• If the allergen cannot be provided in a form that allows it to be used for skin or sIgE testing
• If there is a discrepancy between the medical history and sIgE or skin tests.
• If the skin test could lead to a systemic reaction.
• Before provocation testing is considered to confirm the causative allergen.

For this in-vitro procedure, the basophilic granulocytes are incubated with the relevant allergens (e.g. drugs, insect venom). After allergen stimulation, the basophils are detected by means of an anti-IgE antibody and their degree of activation is determined by the expression of specific surface markers(CD63 or CD203c, see CD classification below) by flow cytometry (see flow cytometry); alternatively, after allergen stimulation, the"leukotriene release" can be measured by ELISA.

Basophil activation is determined from heparin blood. The test is particularly suitable for the quantification of allergic reactions to food components/contents and drugs for which no RAST diagnosis exists.

1. Glässner A et al. (2024) In vitro diagnostics of drug allergies. J Dtsch Dermatol Ges 22 (11):1529-1540.
2. Strohmeier d et al. (2017) Evaluation of the basophil activation test in the diagnosis of food and drug intolerances. Allerg J Int 26: 72-73.