Financial Toxicity in Women with Endometriosis: Psychometric Validation of the Polish COST-FACIT with Analysis of Demographic and Clinical Factors

Background: Endometriosis is a chronic condition associated with substantial healthcare costs, diagnostic delays and long-term impairment in quality of life. Despite the recognized economic burden, patient-reported financial distress remains insufficiently studied. The aim of this study was to adapt and validate the Polish version of the Comprehensive Score for Financial Toxicity (COST-FACIT) for use in women with endometriosis, as well as to examine demographic and clinical factors associated with financial toxicity. Methods: A cross-sectional study was conducted among Polish women with endometriosis using an online survey. The COST-FACIT was adapted following standard forward–backward translation procedures, with FACIT approval. Psychometric evaluation included internal consistency, construct validity, convergent validity with the Financial Well-Being Scale, and test–retest reliability. Exploratory and confirmatory factor analyses were performed, and multivariable models were used to identify factors associated with financial toxicity. Results: The adapted scale demonstrated good psychometric properties, with excellent internal consistency (Cronbach’s α = 0.92; McDonald’s ω = 0.92) and strong test–retest reliability (r = 0.87). Exploratory factor analysis supported a two-factor structure of the instrument. COST-FACIT scores were strongly correlated with financial well-being (r = 0.78). Higher education, stable employment and higher income were associated with better financial well-being, whereas longer symptom duration, greater distance to care and higher healthcare expenditures were associated with worse scores. Conclusions: The Polish COST-FACIT demonstrated good psychometric properties and may serve as a useful instrument for assessing financial toxicity in women with endometriosis. The results highlight the financial burden of the disease and support the use of patient-reported measures to identify individuals at risk of financial distress and reduced quality of life. This tool may facilitate clinical research and improve patient-centered care.