Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation
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A revision of the Quality of Life Questionnaire (QLQ-C30) of the European Organization for Research and Treatment of Cancer (EORTC) was undertaken to improve low internal consistency estimates (Cronbach's alpha) and content validity for the role functioning scale and a conceptual difficulty (undue emphasis on physical functioning) in the global quality of life (QOL) scale. The role functioning items were reworded and a four-category response format was substituted for the previous dichotomous format. A new item asking about 'overall health' was substituted for the 'overall physical condition' item in the global QOL domain. ⋯ In both samples there was a marked improvement in internal consistency for the role functioning scale (Cronbach's alpha s ranging from 0.78-0.88) in the new version. In the global QOL scale, the substitution of the new item for the previous one did not alter internal consistency (Cronbach's alpha's ranging from 0.81-0.92). The revised versions of the role functioning and global QOL domains have been incorporated into the QLQ-C30 (version 2.0).