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

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