Allergen Immunotherapy Adherence in the Real World: How Bad Is It and How Can It Be Improved?

Abstract

Allergen immunotherapy (AIT) is the only available causal treatment for allergic respiratory diseases; however, data demonstrate a high discontinuation rate for both subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT). The complex mechanism of action of allergen immunotherapy (AIT) includes an interaction of innate and adaptive immune processes, resulting in immune tolerance, as illustrated by a decrease in specific immunoglobulin (Ig)-E, an increase in specific IgG1 and IgG4, and inhibition of inflammation involving mast cells, basophils, and eosinophils. This induction of immune tolerance leads to a significant improvement in symptoms and decreased medication scores. A 3- to 5-year course of AIT is required to obtain this disease-modifying effect, which substantially differentiates AIT frompharmacologic treatment. A carry-over effect can persist for up to 12 years. Furthermore, AIT may prevent the onset of asthma in patients with allergic rhinitis, as well as decreasing the onset of new sensitizations to inhalant allergens. Several meta-analyses and controlled studies, involving adult and pediatric subjects, have indicated that both sublingual immunotherapy (SLIT) and subcutaneous immunotherapy (SCIT) are relatively safe, effective, and well tolerated. AIT may also have a positive impact on the cost to the healthcare system, as evidence indicates the cost–benefit of such treatment. Adherence to AIT is crucial for a positive clinical outcome and non-adherence represents a major drawback for such therapy. It actually concerns not only AIT but also various pharmacologic treatments for allergic respiratory diseases, as well as for other chronic illnesses. The issue of non-adherence is an emerging and worldwide problem for chronic diseases and could be an important factor responsible for an overall decrease in treatment efficacy and increased rates of hospitalization, morbidity, and mortality. This review provides an overview of the different reasons that may account for the low adherence rate for AIT. Some of these reasons can be related to the patient’s age when they begin such therapy, the allergic disease being treated, and questions about the efficacy, costs, inconvenience, and safety of AIT. Well-structured educational programs,especially by healthcare professionals, the print media, and the Internet, are needed to improve adherence to AIT.