Evaluation of reliability and validity of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30, Albanian version) among breast cancer patients from Kosovo

Patients and methods: A sample of breast cancer patients (n=62 women) were interviewed for the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) in Albanian. Reliability of the questionnaire was considered acceptable if Cronbach's alpha was >= 0.70. Item convergent-discriminant validity was tested through multitrait scaling analysis. Construct validity was tested under the hypotheses that QLQ-C30 interscale correlations would have an acceptable value of >= 0.40 and as well as by known group comparisons assessing differences of patient subgroups with reference to disease stage and education level. Results: The mean age of the patients was 50 years (standard deviation: 10.9 years). Cronbach's alpha ranged from 0.54 for the cognitive functioning scale to 0.96 for the global health quality of life (GH/QoL) scale. In multitrait scaling analysis, the strength of Spearman's correlations between an item and its own subscale was >= 0.40, with the exception of item 5 (p=0.22); results for item discriminant validity were satisfactory, with the exception of item 5, which showed higher correlation with other subscales than with its own physical functioning. The Spearman's interscale coefficients generally were correlated with each other. Results of known group comparisons did not show significant differences in terms of disease stage. Regarding education level, patients with high school/university education had better functional scales scores only in certain subscales compared to other subgroups; furthermore, patients with secondary school education had better GH/QoL compared to other subgroups of patients. Conclusion: The EORTC QLQ-C30 (v3.0) in Albanian was found to be valid and reliable for women with breast cancer and could be considered as a starting point for further evaluation study.