Influence of time horizon and treatment patterns on cost-effectiveness measures: the case of allergen-specific immunotherapy with Grazax

Summary

This paper investigates the impact of treatment patterns on the cost effectiveness of GRAZAX® (grass allergen tablet) versus standard care in the management of allergic rhinoconjunctivitis in Sweden. Two Grazax treatment patterns are considered: seasonal and World Health Organization (WHO)-recommended specific immunotherapy (SIT). The results are derived from a clinical trial and two model-based analyses. In contrast to the seasonal-use model, the model for WHO-recommended SIT treatment extrapolates the cost of Grazax non-linearly. This is the main methodological distinction between the two analyses. Grazax is cost effective both for WHO-recommended SIT treatment and seasonal treatment, with WHO-recommended SIT treatment being the more cost effective when the time horizon is 6.3 years or more. The time horizon of the analysis becomes a key determinant of the cost effectiveness of Grazax when used as a WHO-recommended SIT treatment.