Adherence and Effect on Allergy Medication Use in Allergic Rhinoconjunctivitis Patients Treated With House Dust Mite Allergen Immunotherapy-A Nationwide Cohort Study.

INTRODUCTION: House dust mite (HDM) allergy significantly impacts quality of life. Allergen immunotherapy (AIT), specifically sublingual immunotherapy (SLIT), is an effective treatment for HDM allergy, but adherence to SLIT remains a challenge. This study aimed to evaluate the impact of adherence to SLIT on the use of allergy medications, including antihistamines, nasal corticosteroids, and inhaled corticosteroids (ICS) in a real-world setting.

METHODS: We conducted a nationwide cohort study using data from Denmark's comprehensive registries. Patients who initiated HDM SLIT between 2015 and 2020 were included, with follow-up through 2022. Adherent patients, defined as those obtaining at least 80% of the prescribed Defined Daily Dose (DDD) of SLIT, were compared to non-adherent patients. Medication use was tracked for antihistamines, nasal corticosteroids, and ICS. Statistical analyses, including Probit and generalised linear models, assessed the likelihood of obtaining medications and the quantity dispensed, adjusted for age and sex.

RESULTS: Of 950 patients, 456 (48%) were classified as adherent. Adherent patients showed significantly reduced usage of antihistamines (p < 0.001) and nasal corticosteroids (p < 0.001) compared to non-adherent patients. No significant differences were found in ICS use or dosage. Additionally, adherent patients were more likely to have higher education levels and be married or cohabiting.

CONCLUSION: Adherence to SLIT for HDM allergy is associated with reduced use of antihistamines and nasal corticosteroids. These findings emphasise the importance of SLIT adherence in managing HDM allergy and suggest that improving adherence could further reduce medication usage, improving patient outcomes in real-world settings.