Are IgE levels to foods other than rosaceae predictive of allergy in lipid transfer protein-hypersensitive patients?

Background: Lipid transfer protein (LTP), the most frequent cause of primary food allergy in Italy, is a cross-reacting plant pan-allergen. Markers able to predict whether a patient sensitized to a certain food but not yet clinically allergic will develop allergy would be extremely helpful. Objective: It was the aim of this study to investigate the relevance of IgE levels to some plant foods other than Rosaceae as predictors of either local or systemic allergic reaction in LTP-allergic subjects. Methods: One hundred (40 males, 60 females , mean age 29 years) peach-allergic patients monosensitized to LTP seen at 14 Italian centres in 2009 were studied. Walnut, hazelnut, peanut, tomato, rice and/or maize allergy was ascertained by interview and confirmed by positive skin prick test. IgE levels to these foods and to rPru p 3 were measured. Results: Higher levels of IgE to Pru p 3 were associated with a higher prevalence of allergy to hazelnut, peanut and walnut. For all study foods, except rice, median IgE levels in allergic subjects significantly exceeded those in tolerant subjects, though within single allergic groups, the differences between patients reporting systemic or local (oral) symptoms were not significant. Ninety-five percent cut-off IgE levels predictive of clinical allergy were established for study foods although the marked overlaps between allergic and tolerant subjects made them of limited usefulness. Conclusion: Specific IgE levels are only partially predictive of clinical allergy. The reasons why some individuals showing low specific IgE levels develop clinical allergy whereas others showing high IgE levels do not, despite similar exposure to the allergen, remain unclear.