When Uncertainty Varies by Language – Psychometric Findings of the Intolerance of Uncertainty Scale (IUS) in Oncology

Abstract: Objective : Intolerance of uncertainty (IU) is central to understanding health anxiety and other pathologies, especially among cancer patients confronted with uncertain prognoses and trajectories. Although the Intolerance of Uncertainty Scale (IUS) is widely used, previous studies have reported different factor solutions and its structure in Persian-speaking cancer populations remains unclear. This study evaluates the psychometric properties of the Persian IUS in cancer patients. A secondary aim explores cross-linguistic differences in factor structures compared to other language versions. Method : A total of 202 patients with solid tumors or hematological malignancies were recruited, 18 incomplete forms were excluded. Exploratory factor analysis (EFA) with parallel analysis was performed, and internal consistency and convergent validity were evaluated. Cross-linguistic comparisons were made with previously published English-language and Lithuanian-language factor solutions. Results : A two-factor model emerged, both showing high internal consistency. Factor correlations supported criterion validity. Contrary to expectations, the Persian version did not converge with other language versions, and the Lithuanian version likewise showed little similarity to either the Persian or English solutions; the two English solutions showed high similarity. These findings suggest that IU may be conceptualized differently across languages and samples. Conclusion : Although scores on the Persian version of the IUS demonstrated good reliability and evidence of criterion validity in this sample of cancer patients, its divergence from both English and Lithuanian models highlights the importance of cultural-linguistic factors in measuring IU. Future studies should investigate invariance across broader samples to clarify potential cross-linguistic differences in the measurement of IU.