Efficacy of Grass Pollen Allergen Sublingual Immunotherapy Tablets for Seasonal Allergic Rhinoconjunctivitis: A Systematic Review and Meta-analysis

IMPORTANCE: Randomized clinical trials (RCTs) and meta-analyses of sublingual immunotherapy (SLIT) for the treatment of seasonal allergic rhinoconjunctivitis (SARC) have shown a modest clinical benefit compared with placebo. Furthermore, indirect comparison by meta-analyses showed that subcutaneous immunotherapy is more effective than SLIT. Despite these data, SLIT has become the most prescribed treatment of SARC in Europe in recent years, and it was approved by the US Food and Drug Administration for the treatment of SARC to grass pollen in the United States on April 1, 2014. OBJECTIVE: To assess the efficacy and safety of the grass pollen sublingual tablets licensed as drugs in the treatment of patients with SARC to grass pollen. DATA SOURCES: Computerized bibliographic searches of MEDLINE, EMBASE, the Cochrane Library, and ClinicalTrials.gov (from inception to April 30, 2014) were supplemented with a manual search of reference lists. STUDY SELECTION: Randomized clinical trials were included if they compared the grass pollen SLIT tablets approved by regulatory authorities in the European Union and the United States for SARC with placebo. DATA EXTRACTION AND SYNTHESIS: Data on populations, interventions, and outcomes were extracted from each RCT according to the intent-to-treat method by 2 independent observers and were combined using the method by DerSimonian and Laird. MAIN OUTCOMES AND MEASURES: The primary end point was the difference in the symptom score and medication score between SLIT and placebo. We pooled data using random-effects meta-analysis, with standardized mean differences (SMDs) and 95% CIs reported. RESULTS: Data were available in 13 RCTs for the symptom score (4659 patients) and in 12 RCTs for the medication score (4558 patients). We found a small treatment benefit in the symptom score (SMD, −0.28; 95% CI, −0.37 to −0.19; P