The COmprehensive Score for financial Toxicity (COST) in China: validation and responsiveness.

CONTEXT: Financial toxicity is a priority concern faced by cancer patients and oncology providers. A validated instrument is important to measure this toxicity and improve health-related quality of life of patients.

OBJECTIVES: To assess the validity and responsiveness of the Chinese version of the COmprehensive Score for financial Toxicity (COST) and to measure financial toxicity using the COST instrument in Chinese healthcare systems.

METHODS: A longitudinal observational study was performed at three cancer centers from March 2017 to October 2018 for eligible patients. Construct validity was assessed by exploratory and confirmatory factor analysis. The convergent and discriminant validity was tested by examining the correlation coefficient. Responsiveness was tested using the standardized response mean and effect size. Associations between the financial toxicity and variables were assessed by multivariable linear analysis.

RESULTS: There were 440 participants at baseline and 268 participants at 6-month follow up. A two-factor solution better represented the Chinese version of COST structure with good internal consistency and test-retest reliability. Convergent validity showed mild to moderate correlations between the domains of COST and the similar domains of Self-Perceived Burden Scale (SPBS) and Quality of Life (QOL) Discriminant validity showed a low correlation between the COST and the subjective support of Social Support Rate Scale (SSRS). Sensitivity to change at the sixth month showed effect sizes with global COST scores of 0.3. Multivariable analysis showed that age, household income and health insurance were significantly associated with financial toxicity.

CONCLUSIONS: The Chinese version of COST is a valid and clinically responsive instrument. The identified baseline variables can be used to provide evidence for a Financial toxicity intervention study..