Sublingual immunotherapy: efficacy – methodology and outcome of clinical trials

Using Medline we identified 39 placebo-controlled, double-blind sublingual immunotherapy (SLIT) studies providing symptom–medication score. These were retrospectively evaluated for evidence of clinical efficacy and quality of study presentation. Clinical efficacy was estimated according to statistical significance and graded as: unequivocal efficacy (statistically significant difference from placebo in both symptom and medication scores or the combined score), which was observed in 28% of studies, possible efficacy (significant improvement in either symptom or medication scores) seen in 33%, and no efficacy (no statistical difference between active treatment and the placebo group), as found in 38% of studies. Generally, studies were limited by the number of patients, showed a high frequency of withdrawals, a short duration of treatment, and insufficient data on randomization. The magnitude of efficacy additional to placebo treatment must be >20% in order to justify the treatment. This review concludes that future SLIT studies should be planned in accordance with international recommendations in order to be conclusive.