Effectiveness of specific immunotherapy in the treatment of asthma: A meta-analysis of prospective, randomized, double-blind, placebo-controlled studies

Background: Despite decades of positive experience with specific immunotherapy (SIT) in the treatment of asthma, outcomes associated with SIT have not been evaluated. Objective: This meta-analysis was conducted to compare the effects of SIT plus medical treatment with those of SIT without medical treatment in patients with asthma. Methods: All studies of SIT in patients with asthma published in English between the years 1966 and 1998 were identified through a MEDLINE® search. All prospective, randomized, double-blind, placebo-controlled studies of SIT identified by the search were included in the meta-analysis. One author (R.N.R.) extracted data from these studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a random-effects model. Results: Data were extracted from 24 identified studies of the clinical effectiveness of SIT in the treatment of asthma, involving 962 asthmatic patients with documented allergy. Immunotherapy was judged effective in 17 (71%) of the 24 studies, ineffective in 4 (17%), and equivocal in 3 (12%) (χ² = 15.25, df = 2, P = 0.0005). Symptoms of asthma were more likely to improve in patients who received SIT than in patients who received placebo (OR 2.76, 95% CI 2.22 to 3.42). Results also favored the immunotherapy group for improvement in pulmonary function (OR 2.87, 95% CI 1.82 to 4.52), protection against bronchial challenge (OR 1.81, 95% CI 1.32 to 2.49), and reduced need for medications (OR 2.00, 95% CI 1.46 to 2.72). Conclusion: The findings of this meta-analysis support the conclusion that SIT is effective in a population of patients with allergen-triggered asthma.