Objective: The purpose of this study was to identify factors associated with increased risk of adverse systemic reactions to cluster allergen immunotherapy and to create a preliminary predictive clinical model.

Methods: In a prospective observational study, the tolerance of 611 patients with seasonal respiratory diseases who were receiving cluster immunotherapy was monitored and all systemic reactions were recorded. Associations between potential prognostic factors (sex, age, respiratory disease, severity, duration of disease, previous immunotherapy, nonseasonal symptoms, skin prick test, total immunoglobulin (Ig) E, specifi c IgE, treatment schedule, allergenic composition, batch, date of treatment, habitat, place of residence) and systemic reactions were estimated. Multivariate stepwise logistic regression analysis was used to build a predictive clinical model and estimate the probability of systemic reactions to cluster immunotherapy.

Results: Sixty-five patients (10.6%) suffered systemic reactions. Only 7 independent risk factors were retained in the fi nal model: age over14 years (odds ratio [OR], 2.6), previous immunotherapy (OR, 0.3), skin prick test positive to Chenopodium album (white goosefoot) (OR, 3.0), elevated specifi c IgE to grass pollen (OR, 2.3), elevated specifi c IgE to olive pollen (OR, 4.1), olive pollen 100% composition (OR, 2.6) and treatment schedule (OR, 1, 1.6 or 7.1, depending on the cluster immunotherapy schedule).

Conclusions: This predictive model, derived from simple clinical variables, has excellent ability to assess individual risk of suffering systemic reactions to cluster allergen immunotherapy. Detecting high-risk patients can help clinicians to prevent and eliminate many severe adverse reactions to cluster immunotherapy.

Key words: Allergen-immunotherapy. Adverse reactions. Rhinitis. Asthma. Pollen. Predictive clinical model.