Analysis of the efficacy of specific immunotherapy with house-dust mite extracts in adults with allergic rhinitis and/or asthma

Background: Allergen specific immunotherapy and allergen reduction are the only therapies in perennial allergic diseases to reduce symptoms in the long term. Specific immunotherapy has the potential to reduce symptoms and the need for medication significantly and furthermore to prevent progression into more severe disease e.g. asthma. Methods: The clinical value of specific immunotherapy has been studied for the last 30 years. We undertook an analysis of clinical trials of subcutaneous specific immunotherapy with Der p or Der f in adults to assess the efficacy of this controversial form of allergy treatment. Results: A computerized bibliographic search revealed 13 randomised double-blind, placebo-controlled trials of specific immunotherapy with Der p/Der f for rhinitis and/or asthma in adults since 1970. The results extracted included patients symptoms, medication requirements, lung function, specific challenge-tests as titrated nasal, conjunctival or bronchial challenge test and side effects. For studies with continuous outcomes as symptom-score and medication score the effect size was obtained by the difference in the scores between the active therapy and the placebo groups. For studies with categorical outcomes as increase or decrease in challenge-tests the results were expressed as odds ratios for improvement against no change and 95% confidence intervals were calculated. Discussion: Focused on the studies after 1980 there was a significant improvement on symptom score and medication score in the actively treated group compared to the placebo group, while the lung function was not significantly altered. Allergen provocation tests reflect the sensitivity of the shock organ. As the documentation of the clinical effects measured by challenge tests shows a highly significant improvement in the actively treated group, we recommend allergen provocation tests as a useful and sensitive parameter during specific immunotherapy. The risk of life-threatening side effects is low, although severe anaphylactic reactions may be, induced. Specific immunotherapy using a standardized house-dust mite extract is effective and safe in adults when administered under optimal conditions.