Psychometric properties of the Chinese version of the functional assessment of chronic illness therapy–fatigue (FACIT–F) among patients with breast cancer

BACKGROUND: Fatigue is the most frequent and distressing symptom affecting the physical, cognitive, and affective domains of breast cancer patients. The Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT–F) has been widely used in patients with chronic diseases and has shown satisfactory reliability and validity. This study aimed to examine the psychometric properties of the FACIT–F among Chinese patients with breast cancer. METHODS: Using a convenience sampling method, a cross–sectional survey (January 2020 and September 2022) was used with patients recruited from two tertiary hospitals in Shanghai, Mainland China, and a total of 597 patients completed a demographic information questionnaire, the FACIT–F and the Functional Assessment of Cancer Therapy for Breast Cancer (FACT–B). Convergent validity was estimated by calculating the Pearson correlation coefficient of the FACIT–F with the FACT–B. Measurement invariance across age was performed by examining differential item functioning (DIF) across age groups (≤ 60 and > 60 years). The internal consistency and split–half reliability were performed for reliability analysis. Unidimensionality of the scale was evaluated by the principal component analysis by Rasch analysis. Additionally, Rasch analysis was performed for item difficulty levels, and an item–person map was used. RESULTS: No floor/ceiling effects were observed for the FACIT–F. Moderate correlations were found between FACIT–F and FACT–B (r = − 0.342, p < 0.01). Most items showed an absence of DIF regarding age, except for one item. In addition, the FACIT–F showed acceptable internal consistency. Principal component analysis of Rasch residuals showed that the proportion of variance explained by the FACIT–F was 53.3%, and the outfit mean square statistics for the items ranged from 0.68 to 1.90 and the infit MNSQ from 0.63 to 1.73. Additionally, an acceptable response between items and persons was found. CONCLUSIONS: The findings indicate that the Chinese version of the FACIT–F is a valid tool for the measurement of fatigue in breast cancer patients.