Scientific Study

Background: Walnut allergy is common across the globe, but data on the involvement of individual walnut components is scarce. Objectives: To identify geographical differences in walnut component sensitization across Europe, explore co-sensitization and cross-reactivity, and assess associations of clinical and serological determinants with severity of walnut allergy. Methods: As part of the EuroPrevall outpatient surveys in 12 European cities, standardized clinical evaluation was conducted in 531 individuals reporting symptoms to walnut, with sensitization to all known walnut components assessed in 202 subjects. Multivariable Lasso regression was applied to investigate predictors for walnut allergy severity. Results: Birch-pollen related walnut sensitization (Jug r 5) dominated in Northern and Central Europe; LTP sensitization (Jug r 3) in Southern Europe. Profilin sensitization (Jug r 7) was prominent throughout Europe. Sensitization to storage proteins (Jug r 1, 2, 4 and 6) was detected in up to 10% of subjects. The walnut components that showed strong correlations with pollen and other foods differed between centres. The combination of determinants best predicting walnut allergy severity were: symptoms upon skin contact with walnut, atopic dermatitis (ever), family history of atopic disease, mugwort pollen allergy, sensitization to cat/dog, positive SPT to walnut, and IgE to Jug r 1, 5, 7 or carbohydrate determinants (AUC = 0.81 [95%-CI 0.73-0.89]). Conclusions: Walnut allergic subjects across Europe show clear geographical differences in walnut component sensitization and co-sensitization patterns. A predictive model combining results from component-based serology testing with results from extract-based testing and information on clinical background, allows for good discrimination between mild-to-moderate and severe walnut allergy.