Determining the minimal important differences in the RQLQ score with grass and tree allergy immunotherapy versus placebo in adults with moderate‐to‐severe allergy

BACKGROUND: Pollen from grasses and trees can trigger allergic rhinitis (AR), where the symptoms and associated consequences can negatively affect quality of life (QoL). The Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) is frequently used in clinical trials of AR to assess QoL. To help interpret RQLQ data, the minimal important difference (MID) can be used to assess whether a mean difference in QoL between treatment groups is clinically meaningful. In seasonal allergy, an MID differs according to the allergen, pollen exposure, symptom severity, patient age and treatment; the same MID cannot be applied to all scenarios. METHODS: Using data from four Phase III clinical trials of SQ sublingual immunotherapy‐tablets in adults with moderate‐to‐severe allergy, between‐group MIDs were derived for the RQLQ in grass pollen allergy (during the peak [n = 501] and entire [n = 514] pollen seasons), and in tree pollen allergy (during the birch [n = 516] and tree [n = 518] pollen seasons), using anchor‐based methodology, supported by distribution‐based methods. RESULTS: For grass pollen allergy, anchor‐based derived between‐group MIDs were 0.22 for the entire pollen season (n = 343) and 0.10 for the peak pollen season (n = 335). For tree pollen allergy, anchor‐based derived between‐group MIDs were 0.26 for the tree pollen season (n = 306) and 0.16 for the birch pollen season (n = 305) (representative of peak season). Distribution‐based derived MIDs were supportive of the anchor‐based values. CONCLUSIONS: This analysis has derived between‐group MIDs specific to the trial populations evaluated and to the conditions under which the data were obtained, and highlights the need for a range of MIDs to reflect the unique nature of seasonal allergic disease.