Measurement properties of the Chinese language version of the functional assessment of cancer therapy-general in a Singaporean population.

INTRODUCTION Health-related quality of life is an important aspect of health outcome. The assessment of it must be done by validated instruments. There is no published data on the validity, reliability and sensitiveness to change of the official Chinese translation of the Functional Assessment of Cancer Therapy-General (version 4; FACT-G). MATERIALS AND METHODS A Chinese questionnaire package comprising the FACT-G and Functional Living Index-Cancer (FLIC, which was translated, modified and validated in Singapore) was filled in by 165 ethnic Chinese patients recruited from the National Cancer Centre, Singapore. Four weeks later, the patients were assessed again by a postal questionnaire survey. RESULTS The FACT-G and FLIC total scores were strongly correlated (r = 0.85). The Physical, Social/Family, Emotional and Functional Well-being scales of the FACT-G converged to and diverged from FLIC components as conceptually expected. The FACT-G and its 4 scales also demonstrated known-groups validity in differentiating patients with different performance status (each P <0.001). Their internal consistency ranged from 0.81 to 0.93 and test-retest reliability ranged from 0.74 to 0.85. The FACT-G and its Physical, Emotional and Functional Well-being scales showed trends of change in relation to change in performance status. The Social/Family Well-being scale was sensitive to decline but not improvement in performance status. CONCLUSIONS The Chinese version of the FACT-G can be used to assess overall level and some specific aspects of health-related quality of life. However, researchers should be cautious in using this instrument to specifically investigate the social aspect of quality of life.