A systematic review and economic evaluation of subcutaneous and sublingual allergen immunotherapy in adults and children with seasonal allergic rhinitis

BACKGROUND: Severe allergic rhinitis uncontrolled by conventional medication can substantially affect quality of life. Immunotherapy involves administering increasing doses of a specific allergen, with the aim of reducing sensitivity and symptomatic reactions. Recent meta-analyses have concluded that both subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) are more effective than placebo in reducing symptoms. It is uncertain which route of administration is more effective and whether or not treatment is cost-effective.

OBJECTIVE: To determine the comparative clinical effectiveness and cost-effectiveness of SCIT and SLIT for seasonal allergic rhinitis in adults and children.

DATA SOURCES: Electronic databases {MEDLINE, EMBASE, The Cochrane Library [Cochrane Central Register of Controlled Trials (CENTRAL)], NHS Economic Evaluation Database (NHS EED)} and trial registries (from inception up to April 2011).

REVIEW METHODS: Standard systematic review methods were used for study selection, data extraction and quality assessment. Double-blind randomised, placebo-controlled trials of SCIT or SLIT, or of SCIT compared with SLIT, and economic evaluations were included. Meta-analysis and indirect comparison meta-analysis and meta-regression were carried out. A new economic model was constructed to estimate cost-utility.

RESULTS: Meta-analyses found statistically significant effects for SCIT and SLIT compared with placebo across a number of outcome measures and for the vast majority of subgroup analyses (type and amount of allergen, duration of treatment). There was less evidence for children, but some results in favour of SLIT were statistically significant. Indirect comparisons did not provide conclusive results in favour of either SCIT or SLIT. Economic modelling suggested that, when compared with symptomatic treatment (ST), both SCIT and SLIT may become cost-effective at a threshold of £20,000-30,000 per quality-adjusted life-year (QALY) from around 6 years, or 5 years for SCIT compared with SLIT (NHS and patient perspective).

LIMITATIONS: It is uncertain to what extent changes in the outcome measures used in the trials translate into clinically meaningful benefits. Cost-effectiveness estimates are based on a simple model, limited data and a number of assumptions, and should be seen as indicative only.

CONCLUSIONS: A benefit from both SCIT and SLIT compared with placebo has been consistently demonstrated, but the extent of this effectiveness in terms of clinical benefit is unclear. Both SCIT and SLIT may be cost-effective compared with ST from around 6 years (threshold of £20,000-30,000 per QALY). Further research is needed to establish the comparative effectiveness of SCIT compared with SLIT and to provide more robust cost-effectiveness estimates.

FUNDING: The National Institute for Health Research Health Technology Assessment programme.