Efficacy of sublingual immunotherapy for cedar pollinosis: A systematic review and meta-analysis.

Background: The efficacy of immunotherapy for cedar pollinosis using a single cedar antigen extract via the sublingual route is uncertain.

Objective: To assess the efficacy of sublingual immunotherapy (SLIT) for patients with cedar pollinosis by performing a systematic review and meta-analysis.

Methods: Randomized clinical trials (RCTs) that compared SLIT with a placebo for patients with cedar pollinosis were searched in the MEDLINE, EMBASE, and Cochrane databases. The primary outcome was the symptom medication score, and secondary outcomes were adverse events, quality of life, and serum IgE and IgG4 levels.

Results: We analyzed 4 RCTs with a total of 762 patients. Meta-analysis revealed that SLIT significantly decreased symptom medication scores compared with placebo groups (standardized mean difference [SMD], -0.94; 95% confidence interval [CI], -1.75 to -0.14; P = .02; I = 93%), and subgroup analysis revealed that SLIT had a significant positive effect on cedar pollinosis when pollen concentration was less (SMD, -2.29; 95% CI, -3.64 to -2.16; P < .001) or more (SMD, -0.36; 95% CI, -0.51 to -0.21; P < .001; I = 0%) than 1,200/cm, and treatment duration was longer than 1 year (SMD, -0.43; 95% CI, -0.59 to -0.26; P < .001; I = 0%). Adverse events were reported in 237 of 405 patients (58.5%) receiving SLIT vs 192 of 357 patients (53.8%) receiving the placebo.

Conclusion: This study revealed a statistically significant benefit of SLIT in patients with cedar pollinosis. However, these findings were based on analysis of a small number of RCTs. Additional large-sample and high-quality RCTs are necessary for further study.