Basophilleucocyte histamine release test

This test assesses the presence of cell-bound specific IgE. It is based upon the measurement of histamine released from antigen-challenged suspensions of leucocytes. Histamine is released from basophils (a type of leucocyte/white blood cell) as a result of the interaction between allergen and cell-bound specific IgE. Histamine can then be isolated with butanol, then acid, and then the concentration can be assessed spectrofluorometrically or by radio-immunoassay. This concentration of histamine is expressed as a percentage of total cellular histamine. This total cellular histamine is assayed following the lysis of a similar number of non-challenged leucocytes with perchloric acid. It may not directly correlate with specific IgE, as other non-IgE mechanisms may cause the degranulation of basophils. There are several drawbacks to this system. The cells need to be extremely fresh, less than 24 hours old, and only a limited number of allergen challenges can be performed on each aliquot of blood. Fifteen per cent of individuals have leucocytes that do not release histamine after undergoing in vitro allergen challenge. There appears to be considerable inter-laboratory variability in the measurement of histamine.32 Advantages include the opportunity to use fresh allergens, rather than processed and potentially altered allergens used in other tests measuring specific IgE. Bindslev-Jensen and Poulsen calculated the clinical sensitivities and specificities of this test in the adults in their one centre.30 They estimated a sensitivity as high as 100% when fresh milk was used as the challenge allergen with a specificity of 87%. The least sensitive measure seems to be as low as 50% with commercially prepared egg and milk. These commercially prepared allergens have specificities of 67% for egg and 100% for milk. This test certainly provides an alternative to immunoassays of specific IgE, in particular for rare food allergens.

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