Double-blind, placebo-controlled food challenge with apple

The aim of the study was to develop and evaluate different methods of doubl e-blind, placebo-controlled food challenge (DBPCFC) with apple. Three diffe rent DBPCFC models were evaluated: fresh apple juice, freshly grated apple, and freeze-dried apple powder. All challenges were performed outside the p ollen season and took place from 1997 to 1999. The freeze-dried apple mater ial was characterized by means of leukocyte histamine release (HR), skin pr ick test (SPT), and immunoblotting experiments. The study population consis ted of birch pollen-allergic patients with a history of rhinitis in the bir ch-pollen season and positive specific IgE to birch. For comparison of the DBPCFC models, 65 patients with a positive open oral challenge with apple w ere selected. In the characterization of the freeze-dried apple material, 4 6 birch pollen-allergic patients were included. The IgE reactivity to apple was evaluated by measurement of specific IgE, HR, and SPT. Golden Deliciou s apples were used in all experiments. The results of this study showed tha t it was possible to perform DBPCFC with apple in birch pollen-allergic ind ividuals. The model with freshly squeezed apple juice had a low sensitivity and displayed a high frequency of reactions to placebo, probably due to th e ingredients used for blinding. The sensitivity of the models with freshly grated apple and freeze-dried apple powder was 0.74/0.60. An increase in s ensitivity is desirable. The freeze-dried apple powder proved to be useful for SPT, HR, and oral challenges, but further investigation of the stabilit y and the allergenic profile of the material is needed.