Basophil allergen threshold sensitivity and component-resolved diagnostics improve hazelnut allergy diagnosis

Background: IgE sensitization to hazelnut is common, especially in birch endemic areas. However, its clinical significance often needs to be confirmed by a food challenge.

Objective: To evaluate the clinical significance of IgE antibodies to hazelnut components and basophil allergen threshold sensitivity (CD-sens) to hazelnut, in relation to double-blind placebo-controlled food challenge (DBPCFC) in children with a suspected hazelnut allergy.

Methods: Forty children underwent a DBPCFC. CD-sens to hazelnut as well as IgE antibodies to hazelnut and its components Cor a 1, Cor a 8, Cor a 9 and Cor a 14 were analysed. Serum tryptase was measured before, during and after DBPCFC.

Results: Eight children had a positive DBPCFC, and all of them had a high CD-sens value to hazelnut. Of the 32 children that passed the DBPCFC, 31 were very low or negative in CD-sens. A positive DBPCFC corresponded with significantly higher CD-sens values (median 8.9, range 3.3-281) compared to children negative in challenge (median 0.05, range 0-34.7, P < 0.0001). Children positive in challenge also had higher levels of IgE-ab to Cor a 9 and Cor a 14 (P < 0.01 and P < 0.001, respectively) compared with those with a negative challenge. In relation to the results from DBPCFC, the sensitivity of CD-sens and IgE-ab to Cor a 14 was excellent (100%) and the specificity was very high (> 97% and > 94%, respectively). Five of the eight patients positive at challenge showed an increase in tryptase > 20% compared to tryptase baseline levels.

Conclusions and clinical relevance: CD-sens and component-resolved diagnostics to hazelnut, used separately or in combination, may improve the diagnostic accuracy and safety and reduce overdiagnosis of hazelnut allergy.