Polish cross-cultural adaptation of the Glasgow Benefit Inventory as an instrument for the post-intervention measurement of change after Gamma Knife treatment.

<b>Introduction:</b> The Glasgow Benefit Inventory (GBI) is one of questionnaires for the measurement of treatment success, which is widely used in patients after vestibular schwannoma treatment.<b>Aim:</b> This study aimed to adapt the GBI originally written in English to Polish conditions and to evaluate its psychometric properties.<b>Material and methods:</b> The Polish version of the GBI used in this study was prepared by a bilingual translator, and its accuracy was ensured by back-translation. To identify the structure of the Polish version of the GBI, exploratory factor analysis was performed. The reliability was determined using Cronbach's α. To verify the validity, correlation analysis was conducted between the domains of GBI and other questionnaires.<b>Results:</b> The results of confirmatory factor analysis indicated that the original 3-factor model is not a good fit for the data. The exploratory factor analysis was performed and identified 4 factors. The total variance of the 4-factor solution was 66.25%. The Cronbach's α calculated for the total GBI reached 0.91. Our analysis confirmed significant weak or moderate correlations between tools for the measurement of general QoL (AQoL-8D: r = 0.411; p = 0.000) and health-related QoL (PANQOL: r = 0.367; p = 0.000; a tool dedicated for patients with VS), well-being (WHO-5: r = 0.432; p = 0.000), hearing and tinnitus (STS: r = -0.217; p = 0.016).<b>Conclusions:</b> This study reports the first adaptation of the GBI for patients with VS to Polish conditions. The results demonstrated that the Polish version of the GBI is a reliable and valid questionnaire that can be used to measure treatment success.