The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30): validation study of the Thai version.

The objective of this study was to assess the psychometric properties of the Thai version of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) version 3.0. The questionnaire was completed by 310 cancer patients during their follow-up at 2 teaching hospital oncology clinics. About 70% of participants had advanced stage of cancer and 72% had been receiving chemotherapy. Cronbach's alpha coefficients of the six scales were above 0.7, except for cognitive and social function scales. All test-retest reliability coefficients were high. Multi trait scaling analysis showed that all item-scale correlation coefficients met the standards of convergent and discriminant validity. Most scales and items could discriminate between subgroups of patients with different clinical status assessed with the Eastern Cooperative Oncology Group (ECOG) scale. The results suggested that the EORTC QLQ-C30 and the Functional Assessment of Cancer Therapy - General (FACT-G) measured different aspects of quality of life and should be independently used. Testing psychometric properties of the EORTC QLQ-C30 in heterogeneous diagnostic group yield similar results as found in homogeneous group. These results support that the EORTC QLQ-C30 (version 3.0) has proven to be a reliable and valid measure of the quality of life in Thai patients with various types of cancer.