Financial Toxicity Following Cancer in a Middle-Income Country with a Pluralistic Health System: Validation of the COST Questionnaire

Background: Financial toxicity is the outcome of the objective financial burden and subjective financial distress experienced by patients receiving cancer treatment. Objective: To validate the English and Malay versions of the COmprehensive Score for financial Toxicity (COST) questionnaire in a multiethnic setting with a pluralistic healthcare system. Intervention/methods: A cross-sectional study was conducted on 720 adults with cancer from public and private hospitals across Malaysia. Reliability was estimated using Cronbach’s α for internal consistency. Construct validity was assessed by exploratory factor analysis. Criterion validity was tested using the European Organization for Research and Treatment of Cancer’s Quality of Life Questionnaire. Results: Overall, 362 respondents answered the English language questionnaire and 358 answered the Malay version. Both versions achieved high reliability (Cronbach’s α: .91 and 0.96, respectively). Exploratory factor analysis via the parallel analysis method identified a single factor solution with eigenvalues of 6.244 and 6.544, explaining 56.80% and 59.50% of variances, respectively. Low positive correlations and strong negative correlations were observed with global health status and financial difficulty, respectively. Subgroup analyses indicated that both versions performed well across diverse patient groups. Conclusion: The English and Malay versions of COST are psychometrically robust in measuring financial toxicity in multiethnic settings with pluralistic health systems and across diverse subgroups of cancer patients with varying clinical characteristics. Implications for Practice: The COST tool should be useful in accurately identifying patients with cancer who experience financial toxicity in Malaysian settings and potentially other similar settings. What is Foundational: Early identification of patients experiencing financial toxicity using validated tools in oncology practice would enable timely intervention.