Validation study of a quality of life (QOL) questionnaire for use in Iran

Abstract

Introduction: 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. The 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 has been translated into many languages and used in various countries. However, version 3.0 has not yet been validated for use with Iranian patients. The aims of the present study were therefore to evaluate the reliability and validity of the new QLQ-C30 questionnaire.

Method: We conducted a cross-sectional study on 132 random samples of breast cancer patients. 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 evaluated convergent and discriminant validity. Clinical validity was evaluated by known-group comparisons. All calculations were performed using SPSS.V.13 software.

Results: In the reliability analysis, most scales fitted the criteria except the fatigue (Alpha 0.65), pain (Alpha 0.69) and nausea and vomiting scales (Alpha 0.66). Convergent validity was evidenced by item own subscale correlation above 0.40 for all multi-item subscales. Item discriminant validity was successful in all analyses except for item 4 of the physical functioning scale. Results of the group based analysis show significant differences in QLQ-C30 functioning and symptom scores, where patients with higher grade have the worst outcome(P<0.05).

Conclusion: The Iranian version of EORTC QLQC30 is a reliable and valid QOL measure for cancer patients which indicates that it can be used in clinical and epidemiological cancer research.