Armaghane Danesh Bimonthly Journal (Jul 2007)
Reliability and Validity of the QLQ-C30 Questionnaire in Cancer Patients
Abstract
Introduction & Objective: Recently, it has been recognized that a more comprehensive assessment of the cancer patient is necessary and that the evaluation of outcomes must move beyond traditional biomedical endpoints to include assessments of the impact of disease and its treatment on patients' quality of life. European Organization for Research and Treatment of Cancer has developed a 30-item quality of life questionnaire to obtain information about the impact of disease and treatment on the daily living of cancer patients. This questionnaire was translated into many languages and used in various countries. But, validity and reliability of version 3.0 has not yet been checked for use with Iranian patients. The aims of the present study are to evaluate the reliability and validity of the QLQ-C30 (version 3.0) questionnaire. Materials & Methods: We conducted an analytical cross-sectional study on 132 random samples of breast cancer patients for determination of validity and reliability of QLQ-C30 (version 3.0) questionnaire. The questionnaire was completed for all patients that referred to chemotherapy ward in Namazi Hospital, Shiraz, during 19 Dec 2005 -19 Feb 2006. Reliability was evaluated through the internal consistency of multi-item subscales. Pearson’s correlations of an item with its own scale (corrected for overlap) and other scales were calculated to evaluate convergent and discriminate validity. Clinical validity was evaluated by known-group comparisons using ANOVA and Kruskal Wallis tests. Data were then analyzed with SPSS software. Results: In the reliability analysis, most scales fitted the criteria (Alpha>0.70) except the fatigue, pain, nausea and vomiting scales. Convergent validity was evidenced by item own subscale correlation above 0.40 for all multi-item subscales. Item discriminate validity was successful in all analyses except for item 4 of the physical functioning scale. Results of the known group based analysis show significant differences in QLQ-C30 functioning and symptom scores, where patients with higher grade have the worst (p<0.05). Conclusion: Iranian version of EORTC QLQC30 is a reliable and valid QOL measure for cancer patients which indicate that it can be used in clinical and epidemiological cancer studies.
