Specific immunotherapy for respiratory allergy: state of the art according to current meta-analyses

To evaluate the efficacy of allergen specific immunotherapy in the treatment of allergic asthma and rhinitis as derived by the available meta-analyses.

Electronic databases were searched up to April 30, 2008, for meta-analyses of randomized, placebo-controlled trials assessing specific immunotherapy in respiratory allergy. We looked for studies that evaluated effects on symptom scores and use of rescue medication.

If 2 or more reviews evaluated the same subject, we selected the study with the larger number of patients. We evaluated the quality of individual meta-analyses by following the recommendations of the Cochrane Collaboration and the QUOROM (Quality of Reporting of Meta-analyses) statement.

Seven of 13 meta-analyses met the inclusion criteria: 5 evaluating sublingual immunotherapy and 2 evaluating subcutaneous immunotherapy. All 7 meta-analyses reported a reduction in symptom and medication scores, although 1 sublingual immunotherapy meta-analysis did not find a significant size effect, probably because of the inclusion criteria. Heterogeneity was significant in all 7 included reviews, and standardized mean differences using the random-effects model were adopted.

According to evidence-based criteria, specific immunotherapy can be recommended for the treatment of respiratory allergy because of its efficacy in reducing asthma and rhinitis symptoms. Also, future methodological approaches that consider safety and costs should corroborate this positive evaluation.