Published Online: November 19, 2014
Allergic rhinitis (AR) with or without conjunctivitis (ARC) is a global health problem. Symptomatic treatment is available, but some patients do not tolerate or respond well to these treatments—and only allergen immunotherapy offers persistent, long-term benefits. In clinical practice, subcutaneous allergen immunotherapy (SCIT) and sublingual allergen immunotherapy (SLIT) are the most common methods used to administer products, and efficacy of both SCIT and SLIT compared with placebo has been established. However, direct head-to-head comparisons of SCIT versus SLIT-tablets or SLIT-drops are sparse and have yielded conflicting results. Recently published systematic review articles and meta-analyses have compared the efficacy of these different treatment methods, but conclusions have been mixed.
In an article recently published in The Journal of Allergy and Clinical Immunology: In Practice, Nelson and colleagues performed a network meta-analysis focused specifically on the response to allergen immunotherapy for grass pollen using products which are commercially available in at least one country, with attention to symptom and medication scores specific to the first pollen season following treatment initiation.
The authors conducted a comprehensive and systematic literature review to identify double-blind randomized placebo- or actively- controlled trials reporting AR/ARC symptom and medication use scores. Data extracted from eligible studies were used to perform direct comparisons of each form of allergen immunotherapy to placebo along with indirect comparisons of the relative pair-wise treatment effect between SCIT, SLIT-tablets and SLIT-drop.
This network meta-analysis included 37 studies (14 SLIT-tablet, 14 SLIT-drop and 9 SCIT) with 7759 total patients (4016 treated with immunotherapy and 3743 treated with placebo). Direct comparisons versus placebo from both the pair-wise and network analysis illustrated that SCIT and SLIT-tablet are both significantly superior to placebo for reducing symptom and medication scores. Results for the direct and indirect comparisons of SLIT-drop versus placebo were less definitive for symptom scores but indicated benefit of SLIT-drop on medication use. However, there were no significant differences in symptom score or medication use comparisons between SCIT and SLIT tablets, SCIT and SLIT drops, or SLIT tablets and SLIT drops. In children, the indirect comparison of effects on symptom scores between SLIT-tablets and SLIT-drops favored the tablets.
This study indicates that the effect of SLIT-tablet is similar to SCIT in controlling AR/ARC symptoms, and in the reduction of AR/ARC medication use. In the absence of head-to-head trials, which would be difficult to conduct for these treatments, indirect methodology provides useful evidence of the difference in treatment effects. These data can assist clinicians with identifying the most suitable treatment option for their patients given the choice of AIT formulation for grass allergy.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.