Risk stratification of systemic allergic reactions during Hymenoptera venom immunotherapy buildup phase

Abstract

Background: Comparability of previous studies assessing the incidence of systemic reactions during Hymenoptera venom immunotherapy (VIT) is impaired by methodical differences concerning the definition and classification of VIT-induced anaphylaxis. Our study aims to systematically evaluate the time course and clinical symptoms of VIT-related systemic reactions.

Patients and methods: 12-year data on 818 buildup cycles including 8,504 single injections were retrieved from detailed inpatient treatment protocols. The severity of VIT-related anaphylaxis was graded according to a system proposed by the World Allergy Organization in 2010.

Results: Objective allergic reactions occurred in 28 (3.4 %) buildup cycles; treatment with antihistamines and/or corticosteroids was invariably effective. 23 exclusively cutaneous reactions occurred after a median time interval of 60 minutes (5-480 min.) following the last injection. 0.6 % of the buildup cycles were complicated by moderate to severe anaphylaxis, which occurred more rapidly than mere urticaria and predominantly during honeybee VIT. Patients with moderate to severe anaphylaxis more frequently reported severe index sting reactions and had higher baseline serum tryptase concentrations.

Conclusions: Objective allergic reactions during VIT are rare, and severe anaphylaxis is extremely rare. The use of a consistent classification system for VIT-induced systemic reactions is required to identify risk factors not only for their general incidence, but also for the exceptionally severe anaphylactic reactions.