Persistence, severity and reactivity thresholds in fish allergic patients sensitized to parvalbumin.

Background: Fish allergy affects children and adults worldwide and there are transient and persistent phenotypes.

Objective: We aimed to analyze persistence, severity and reactivity thresholds in challenge-confirmed fish allergic patients sensitized to parvalbumin.

Methods: Patients 12-65 years-old reporting immediate reactions to fish, with fish skin prick test ≥5 mm and IgE to cod and carp β-parvalbumins ≥0.70 kU_A/L were recruited in 6 European centers. Except if recent severe anaphylaxis, patients were eligible for a double-blind placebo-controlled food challenge with cod, followed, if negative, by an open food challenge. Severity of reported and elicited reactions was graded with FASS, eliciting dose (ED) was calculated using interval-censoring survival analysis and probabilistic models, and factors associated with a positive challenge and severe reactions were analyzed by logistic regression.

Results: Out of 42 patients fulfilling inclusion criteria, fish allergy was confirmed in 30 (71.4%). The median fish allergy duration was 23 yr. Although 70% of cases reported anaphylaxis with respiratory or cardiovascular involvement, food challenges resulted in oropharyngeal symptoms (34.7%) or mild systemic reactions (73.9%), with only 1 anaphylaxis with bronchospasm (4.3%). Male sex was associated with severe reactions (OR 5.44, 95%CI 1.04-28.53). ED₁₀ for objective symptoms range was 0.99-2.54 mg protein. No correlation was found between severity and ED.

Conclusion: Adolescents and adults with persistent fish allergy linked to parvalbumin sensitization have experienced severe allergic reactions in real life and have a low threshold of reactivity. Our findings support the need for large-scale studies and new therapeutic options for these fish allergic patients.