Evidence of the efficacy and safety of house dust mite subcutaneous immunotherapy in elderly allergic rhinitis patients: a randomized, double-blind placebo-controlled trial

Background Allergen specific immunotherapy (AIT) in elderly patients is controversial, and there is still little evidence supporting the safety and efficacy of this treatment in this population. The study objective was to evaluate the safety and efficacy of AIT for house dust mite allergens in patients over 65 years of age with allergic rhinitis (AR) and a documented allergy to house dust mites. The primary endpoint was the change from baseline in the mean average adjusted symptom score (AAdSS) and the total combined rhinitis score (TCRS) difference in the least square means for the label compared to placebo. Methods Fifty-eight AR elderly patients who were monosensitized to house dust mites were individually randomized in comparable numbers to one of two parallel groups with the following interventions: 2 years of perennial AIT using PURETHAL Mites or placebo. The symptoms and medication scores were presented as the AAdSS and TCRS. Quality of life, based on the rhinoconjunctivitis quality of life questionnaire (RQLQ), nasal allergen provocation responsiveness, serum allergen-specific IgG4 to D. pteronyssinus and D. farinae and Der p1 and Der p2 were monitored. The intent-to-treat population was analysed. Results After 24 months of AIT, AAdSS significantly decreased from 4.27 ± 1.58 to 1.82 ± 0.71 (p < 0.05). The TCRS was significantly decreased after 2 years of AIT. Serum-specific IgG4 against D. pteronyssinus, D. farinae, Der p1, and Der p2 increased during the AIT trial in the study group. The RQLQ score was significantly improved in patients who received AIT, from 1.86 (95% CI 1.51-1.78) to 1.26 (95% CI 1.09-1.55). Two mild systemic anaphylactic reactions (degree I) were reported after injections in the active group during the AIT therapy. Conclusion The DBPC trial showed AIT for house dust mite allergens was effective and safe in elderly patients with allergic rhinitis. Trial registration This randomized, double-blinded placebo-controlled (DBPC) trial was conducted at one centre (ClinicalTrials.gov no. NCT03209245).