Psychometric properties and measurement equivalence of the English and Chinese versions of the functional assessment of cancer therapy-cognitive in Asian patients with breast cancer.

OBJECTIVE: This study was designed to examine the psychometric properties and measurement equivalence of the English and Chinese versions of the Functional Assessment of Cancer Therapy-Cognitive Function (Version 3) (FACT-Cog) in multiethnic Asian patients with breast cancer.

METHODS: This prospective study involved patients with breast cancer from the National Cancer Centre Singapore. The concurrent validity of the FACT-Cog was assessed according to its strength of correlation with the validated European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire 30 cognitive functioning scale, and its association with fatigue, global health status, and anxiety. The known-group validity was assessed on the basis of receipt of chemotherapy. Factor analysis was conducted to ascertain the one-factor structure of each cognitive domain. The reliability was evaluated by using Cronbach's alpha and intraclass correlation coefficient within the cognitive domains. Multiple regression analyses were performed to compare the total scores between the two language versions, adjusting for covariates.

RESULTS: A total of 185 English-speaking and 143 Chinese-speaking patients were recruited. Both the English and Chinese FACT-Cog total scores correlated strongly with the European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire 30 cognitive functioning scale scores (r = 0.725 and 0.646), whereas correlations with fatigue, anxiety, and global health status were weak to moderate (|r| = 0.376-0.589). Regarding the known-group validity, more severe perceived cognitive disturbance was observed among patients receiving chemotherapy than among those who were not for both versions (P = .010 and .008, respectively). Internal consistencies within the cognitive domains were high (Cronbach's α 0.707-0.929), and test-retest reliability was satisfactory for both versions (intraclass correlation coefficient 0.762 and 0.697). The measurement equivalence between the English and Chinese versions was established for all domains except the multitasking domain.

CONCLUSION: The English and Chinese versions of the FACT-Cog are valid, reliable, and equivalent for clinical and research use.