Effect of specific immunotherapy added to pharmacologic treatment and allergen avoidance in asthmatic patients allergic to house dust mite.

Background: Although several studies support the efficacy of specific immunotherapy in allergic asthma, its benefit compared with that of standardized pharmacologic intervention remains unknown.
Objective: A double-blind, placebo-controlled trial in 72 patients with mild-to-moderate asthma and allergy to house dust mite (HDM; Dermatophagoides species) was conducted to assess the effects of specific immunotherapy added to guideline-adjusted pharmacologic treatment and allergen avoidance.
Methods: After 1 observational year of pharmacologic treatment and standard measures of HDM avoidance, 2 groups of asthmatic subjects were randomly assigned to receive specific immunotherapy consisting of subcutaneous injections of either a mixture of Dermatophagoides pteronyssinus and Dermatophagoides farinae vaccine (n=41) or placebo (n=31) for 3 years. Medications were adjusted every 3 months according to the Global Initiative for Asthma guidelines.
Results: The adjustment of treatment was associated with a reduction in asthma symptom scores in all subjects. The addition of specific immunotherapy was associated with a decrease in the number of subjects requiring rescue bronchodilators, an increase in morning and evening peak expiratory flow, and a reduced skin sensitivity to HDM extracts. The addition of specific immunotherapy had no significant effects on the cumulative dose of inhaled corticosteroids, asthma symptoms, lung volumes, or bronchial responsiveness to methacholine.
Conclusion: These results suggest that specific immunotherapy added to pharmacologic treatment and HDM avoidance provides marginal but statistically significant clinical benefits, possibly by reducing the allergic response of asthmatic patients sensitized to HDM.