Cross-cultural validation of an international questionnaire, the General Measure of the Functional Assessment of Cancer Therapy scale (FACT-G), for Japanese

The General Measure of the Functional Assessment of Cancer Therapy scale (FACT-G) was developed in an English-speaking culture (USA). To determine if FACT-G could be used in Japan, a cross-cultural validation was performed. The Japanese version was created through an iterative forward-backward translation sequence used throughout the FACT multi-lingual translation project. In evaluating psychometric testing, its construct validity was investigated by factor analysis and multi-trait scaling analysis. Clinical validity was estimated by known-groups comparison using stage, performance score (PS) and patient location, and validated longitudinally by PS. The FACT-G (version 3) was given to 180 patients with lung cancer. Analyses showed that the scales of Physical, Functional, Emotional Well-Being, and Relationship with Doctors were constructively valid in Japan. Japanese patients felt that familial relationships were different than those with friends and neighbors, indicating that the Social/Family Well-Being scale needed cultural adaptation. Two items concerning coping with illness and acceptance of illness did not load predictably onto their respective scales and were considered to be cross-culturally problematic. However, clinical validity demonstrated its sensitivity. Japanese version 4 has been improved to address the weakness in an attempt to become an instrument that is applicable across cultures.