Unraveling Kiwifruit Allergy Diagnosis: Usefulness of the Current Diagnostic Tests
Objectives: To determine the usefulness of the in vitro and in vivo methods used in the diagnosis of kiwifruit allergy, focusing on the impact of the seed proteins on their sensitivity. Methods: Skin prick tests (SPTs) using different commercial extracts, homemade pulp and seed extracts, and prick-prick test with kiwifruit were performed on 36 allergic patients. The presence of specific IgE (sIgE) was assessed using ImmunoCAP (kiwifruit extract), ELISA (Act d 1, Act d 2), ISAC and FABER assays. Immunoblotting of seed extract was carried out, and a single blinded oral food challenge with whole seeds was performed in seed-sensitized subjects. Results: The prick prick test with kiwifruit demonstrated the highest diagnostic capacity (81.8% sensitivity and 94.1% specificity) among the in vivo tests. The sIgE levels measured by ImmunoCAP-kiwifruit extract showed a similar sensitivity to that of global ISAC and FABER (63.9%, 59.5% and 58.3%, respectively). Act d 1 was the major allergen, and sensitization to it was associated with positive sIgE to whole kiwifruit extract detected by ImmunoCAP (p <0.000). A positive SPT with kiwifruit seeds was associated with severe symptoms with kiwifruit (p = 0.019) as a marker of an advanced disease, but not with clinically relevant sensitization. The challenge to kiwifruit seeds performed on eight seed-sensitized patients resulted negative. Conclusions: Sensitization to Act d 1 is related to a positive result in conventional diagnostic techniques, whereas kiwifruit seed sensitization.