Re-Validation of the COmprehensive Score for Financial Toxicity (COST): Assessing the Scale's Utility in Chronic Disease Populations

OBJECTIVE: To report the psychometric properties of the COmprehensive Score for financial Toxicity (COST) patient-reported outcome measure (PROM), an 11-item scale previously validated among patients diagnosed with cancer and receiving chemotherapy. METHODS : Data come from a cross-sectional survey (n = 2755 response rate of 87%) of participants in a remote digital health coaching intervention collected between January 2017 and February 2019. RESULTS : COST demonstrated very good internal consistency (Cronbach's alpha =.89) and good convergent validity. Lower financial toxicity was associated with improved physical and mental well- being HRQOL measures after controlling for covariates (b = 0.13, P <.0001; b = 0.28, P <.0001, respectively). Supplemental analyses indicated that the COST instrument loaded on 2 factors. CONCLUSIONS: The COST measure of financial toxicity has good internal consistency and predictive validity in a sample of patients with chronic conditions. However, contrary to previous research examining the psychometric properties of COST in a sample of individuals with cancer, which found COST to be unidimensional, our analyses indicated that the COST measure of financial toxicity is multidimensional in a sample of individuals with chronic conditions. In particular, the items that asked about "general financial wellbeing" loaded on the second factor while "illness-related financial wellbeing" loaded on the first.