Validity and reliability of the European Organization for Research and Treatment in Cancer Quality of Life Questionnaire (EORTC QLQ): experience from Kuwait using a sample of women with breast cancer

BACKGROUND AND OBJECTIVES: Although the EORTC QLQ-C30 and its breast-specific module (BR-23) are widely used instruments, the few reports on their psychometric characteristics from Arab and neighboring countries involved limited analyses. Our objective was to assess the psychometric characteristics of both questionnaires using the responses of a larger sample of Arab women. METHODS: Participants were consecutive clinic attendees at the Kuwait Cancer Control Center. The indices assessed were alpha coefficients, item-internal consistency (IIC), item-discriminant validity (IDV), and known-groups validity. RESULTS: The 348 women were aged 48.3 (10.3) years. The intra-class correlation for the test-retest statistic and the internal consistency values for the multi-item scales were >0.7 alpha. With the exception of the pain subscale, all items met the IIC criterion of >0.4 correlation with the corresponding scale. For IDV, the BR-23 performed better than the QLQ-C30. The scale scores discriminated between patients at different disease stages, and between sick and well populations. CONCLUSION: With the exception of the pain subscale, the Arabic version of the questionnaires is psychometrically sound.