Prevalence of Pol d 1 Sensitization in Polistes dominula Allergy and Its Diagnostic Role in Vespid Double-Positivity

Background: Stings by Polistes species frequently cause allergic reactions. However, standard allergy diagnostics are often unable to differentiate between primary sensitization and cross-reactivity in case of Vespula/Polistes double-sensitization because antigen 5 is the only Polistes venom molecule currently available in diagnostics (Pol d 5). Objective: To evaluate the frequency of phospholipase A1 in Polistes venom allergy (Pol d 1) and its diagnostic role in vespid allergy. Methods: We performed component-resolved diagnostics in patients with vespid allergic reactions who were positive to Polistes venom. A prevalence analysis was performed and the diagnostic accuracy of Pol d 1 was evaluated to detect primary Polistes sensitization in double-sensitized patients. Results: Blood samples were collected from 132 patients. Pol d 1 was present in 97% to 100% of 128 Polistes-positive patients. It was frequently involved in case of positivity to a single Polistes molecule (48% in double- and 80% in mono-sensitized patients). Furthermore, Pol d 1 was positive in 95% of Pol d 5-negative subjects. The diagnostic accuracy of Pol d 1 was good (folded type: area under the curve = 87%; 82% sensitivity and 77% specificity at the best cutoff of 5.773), and even better when used combined with the whole extract ratio (area under the curve = 99%; 91% sensitivity and 100% specificity). Conclusions: The study shows that Pol d 1 is the most frequent Polistes allergen in Italian patients. It can distinguish Polistes primary sensitizations with good diagnostic accuracy, which supports its use in clinical practice.