D3.188 - Real-Life Effectiveness of Subcutaneous Allergen Immunotherapy Assessed by Medication Consumption: A Retrospective Cohort Study

Subcutaneous allergen immunotherapy (SCIT) is an established disease-modifying treatment for allergic rhinitis and asthma. In real-world clinical practice, objective assessment of treatment effectiveness is often challenging, particularly in retrospective settings where data may be unavailable. Medication-based outcome measures may represent a pragmatic alternative to evaluate clinical benefit. This study aimed to assess the impact of SCIT on the annual consumption of medication for allergic rhinitis/rhinoconjunctivitis and asthma in a real-life cohort.

A retrospective observational study was conducted including 37 patients receiving subcutaneous allergen immunotherapy (SCIT) with standardized polymerized aeroallergen extracts (Poliplus®, Roxall, Spain) for at least 24 months. Demographic and clinical data were collected, including age at SCIT initiation and underlying allergic diagnoses. Medication consumption for allergic rhinitis/rhinoconjunctivitis and asthma was assessed as the annual number of dispensed medication packages. For each patient, medication use during the 12 months preceding SCIT initiation was compared with the 12 months following completion of the first year of SCIT. Paired comparisons were performed using the Wilcoxon signed-rank test.

The mean age at SCIT initiation was 20.9 ± 10.1 years. A significant reduction in medication use after SCIT was observed for oral antihistamines (mean 3.32 vs 2.11 packages/year; p<0.001), intranasal corticosteroids ± intranasal antihistamines combinations (mean 2.84 vs 1.43; p<0.001) and leukotriene receptor antagonists (mean 4.59 vs 2.44; p=0.004). No significant differences were found for anti-allergic eye drops (p=0.655). Among patients with asthma, significant reductions were observed in short-acting β₂-agonists (mean 0.77 vs 0.05; p=0.004) and inhaled corticosteroids + long-acting β₂-agonists combinations (mean 4.05 vs 2.55; p=0.002).

In this real-world cohort, SCIT led to a clinically meaningful and statistically significant reduction in the use of both symptomatic and controller medication for allergic rhinitis/rhinoconjunctivitis and asthma. These benefits were already evident after completion of the first year of treatment, reinforcing the disease-modifying effect of SCIT and highlighting its potential to reduce long-term pharmacological burden from the early phases of therapy.