Objective functional tests for the diagnosis of food allergy

To date the diagnosis of gastrointestinal allergy is difficult to confirm, especially when a clear association between food intake and onset of clinical symptoms is lacking. In addition, history, skin tests and IgE-detection in serum are only of limited value and the performance of double-blind, placebo-controlled oral food challenge procedures is time-consuming and cost-intensive. Apart from routine standard allergological tests, determination of (methyl)-histamine in urine is recommended as screening test fur the detection of persons with manifest food allergy. Such allergic individuals are characterised by significantly higher urine mediator levels than controls. The endoscopic identification and quantitation of intestinal allergic inflammation is achieved by measurement of specific mediators (tryptase, eosinophilic cationic protein, TNF) from intestinal tissue. Tissue mediator content was found to be significantly enhanced in gastrointestinal allergy. Tryptase determination from gut mucosa provides a positive predictive value of approximately 90% to identify food-sensitive allergic individuals. Appropriate mucosa oxygenation of intact mucosal particles has been proven to allow functional release experiments by specific mediators. Incubation of biopsies with food challenge-positive antigens leads to significantly increased rates of mediator secretion, whereas tolerated antigens differ not from spontaneous release. This functional release experiments are used for allergen identification, since the results of mucosa oxygenation can predict the outcome of oral food challenge tests with a sensitivity of 78% and specificity of 100% (ECP). The antigen-induced mediator release is classified as immunologic mechanism, when antigen-specific immune phenomena or locally produced intestinal IgE-antibodies (endoscopic lavage) are found in skin-or RAST-tests, or intestinal lavage, respectively.