Allergen components in diagnosing childhood hazelnut allergy: Systematic literature review and meta‐analysis

Abstract

Background Hazelnut‐specific IgE antibodies (sIgEs) in serum support the diagnosis of hazelnut allergy, but extract‐based tests have low diagnostic specificity, commonly leading to over‐diagnosis. Measuring sensitization to individual allergen components may enhance the diagnosis of hazelnut allergy. We systematically examined data on diagnostic accuracy of sIgE to commercially available hazelnut components to compare their individual contributions in diagnosing hazelnut allergy. Methods Seven databases were searched for diagnostic studies on patients suspected of having hazelnut allergy. Studies employing component‐specific IgE testing on patients whose final diagnosis was determined by oral food challenges were included in the meta‐analysis. Study quality was assessed as recommended by Cochrane. Results Seven cross‐sectional studies and one case‐control study were identified, seven presenting data on children (N = 635), and one on a mixed age population. Overall, the diagnostic accuracies of sIgE to both Cor a 9 and Cor a 14 were significantly higher than for Cor a 1‐sIgE (P < .05). In children, the specificity of Cor a 14‐sIgE at 0.35 kUA/L cutoff was 81.7% (95% CI 77.1, 85.6), and 67.3% (60.3, 73.6) for Cor a 9‐sIgE. The specificities for Cor a 1‐sIgE and hazelnut‐sIgE were 22.5% (7.4, 51.2) and 10.8% (3.4, 29.8), respectively. The sensitivity of Cor a 1‐sIgE (60.2% [46.9, 72.2]) was lower than for hazelnut extract‐sIgE (95.7% [88.7, 98.5]), while their specificities did not differ significantly. Conclusion sIgE to Cor a 14 and Cor a 9 hazelnut storage proteins increases diagnostic specificity in assessing hazelnut allergy in children. The combined use of hazelnut extract and hazelnut storage proteins may improve diagnostic value.

Component-Resolved Diagnosis of Hazelnut Allergy in Children

“…Children with positive Cor a 14 sIgE were at higher risk of having hazelnut allergies than those with positive Cor a 9 sIgE, but the difference was not significant. To our knowledge, only one systematic review with metanalysis about hazelnut allergy testing has been published until now (24). In agreement with our results, it found that the diagnostic accuracy of sIgE to Cor a 1 was lower than that of Cor a9 sIgE and Cor a 14 sIgE.…”

“…If a study missed some information necessary to meet the inclusion criteria, authors were contacted. Where we received no response, we used data previously provided by the authors to other reviewers [24]. No language restrictions for included studies were applied: literature in languages other than English has been translated.…”

Sensitization to storage proteins in peanut and hazelnut is associated with higher levels of inflammatory markers in asthma

“…Patients with birch pollen-associated hazelnut allergy are sensitized to Cor a 1 and usually present with mild oral symptoms [12,13]. IgE against the storage proteins Cor a 9 and Cor a 14, both major hazelnut allergens, can be used as markers for primary hazelnut sensitization and risk of more severe reactions [14,15].…”

Allergy to walnuts and hazelnuts in atopic dermatitis patients and analysis of sensitization to molecular components

“…Patients, reporting hazelnut allergy (n = 423) from 12 European cities, were tested for IgE against individual hazelnut allergens; a model, combining CRD with clinical background and extract-based serology, was superior to CRD alone in assessing the risk of severe reactions to hazelnut, particular in ruling out severe reactions (Datema et al (2018 Mar)). Some studies show that sIgE to hazelnut storage proteins, Cor a 14 and Cor a 9, confers higher specificity in the diagnosis of hazelnut allergy in children compared with Cor a 1 or hazelnut extract, and could be used clinically to improve the identification of allergic children and reduce the number of confirmatory food challenges, (Nilsson et al (2020 Feb)); according to the authors, future analyses of the contribution of additional hazelnut allergen components are needed, as well as evaluations in adult populations (Nilsson et al (2020 Feb)). The sensitivity and specificity of both Cor a 9 and Cor a 14-sIgE were consistent across paediatric studies, and the diagnostic parameters calculated showed low data variation.…”