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.

MATERIAL AND 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.

CONCLUSION

Sensitization to Act d 1 is related to a positive result in conventional diagnostic techniques, whereas kiwifruit seed sensitization does not increase the sensitivity of the evaluated diagnostic techniques.