Do corresponding subscales of Quality Of Life instruments measure similar aspects?
In this issue Kuenstner and colleagues investigate this question using questionnaires received from 234 cancer patients. The questionnaires were sent in two waves; the first set comparing the European Organization for the Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (QLQ-C30) and SF-36 Quality of Life (QoL) instruments and the second set comparing the EORTC QLQ-C30 and the Functional Living Index Cancer (FLIC) QoL instruments. Seven dimensions were assessed using a multi-trait, multi-method analysis. In 5 of these 7 dimensions, (physical functioning, emotional functioning, pain, fatigue/vitality and nausea and vomiting) convergent validity exceeded the corresponding correlations of discriminant validity. This infers that for these subscales the three instruments are measuring similar aspects of the patients quality of life. In contrast, the data suggested that the overall health and social functioning subscales of the different instruments can not be equa
