Development and Validation Features of the Patient Benefit Index for the Treatment of Allergic Rhinoconjunctivitis with Allergen Immunotherapy

Purpose: Allergic rhinoconjunctivitis (ARC) is one of the most common diseases worldwide. Allergen immunotherapy (AIT) is the only causal treatment available so far. Due to health policy provisions, the assessment of treatment benefit from the patient's perspective is of high relevance. To date, no instrument for assessing treatment needs and benefits of patients with ARC who receive AIT has been published. The aim of the study was to validate an instrument to assess the patient-relevant treatment benefit of patients with ARC who receive AIT. Methods: We developed the Patient Benefit Index questionnaire for AIT (PBI-AIT), consisting of 33 items. Longitudinal data of patients with ARC were used to test feasibility, reliability and validity. The PBI was compared between the beginning of the study (t1) and the end of the study (t5). Results: N = 279 patients with AIT completed the PBI-AIT at t1, n = 333 at t5; n = 226 at both timepoints. Mean number of missing values per patient was 0.7 in the Patient Needs Questionnaire (PNQ) at t1 and 1.2 in the Patient Benefit Questionnaire (PBQ) at t5. The internal consistencies measured by Cronbach's alpha were 0.98 (PNQ) and 0.99 (PBQ). The mean PBI of the patients with AIT was significantly lower at t1 and improved at t5. The PBI-AIT correlated with all tested external criteria at t5. The correlation between PBI-AIT and satisfaction with previous treatment (r = -0.57, p < 0.001) was higher than the correlation between PBI-AIT and current disease severity (r = -0.26, p < 0.001). Conclusion: The results indicate feasibility, reliability, convergent and discriminant validity as well as sensitivity to change of the PBI-AIT.