Is it useful to calculate sum scores of the quality of life questionnaire EORTC QLQ-C30?

HINZ A., EINENKEL J., BRIEST S., STOLZENBURG J.-U., PAPSDORF K. & SINGER S. (2012) European Journal of Cancer Care 21, 677-683 Is it useful to calculate sum scores of the quality of life questionnaire EORTC QLQ-C30? The aim of this paper is to test the psychometric properties of sum scores of the quality of life questionnaire EORTC QLQ-C30. A sample of cancer patients (n = 1529) and a sample of the general population (n = 1185) were tested with the EORTC QLQ-C30, the Hospital Anxiety and Depression Scale and the Multidimensional Fatigue Inventory. Three sum scores of the EORTC QLQ-C30 are defined: a score concerning functioning, a score concerning symptoms and a total score. Compared with the two-item quality of life scale of the EORTC QLQ-C30, the psychometric quality of the total score and the functioning score is superior with respect to reliability, convergent validity and discriminant validity. Cronbach's alpha of the total score is 0.94 (cancer patients) and 0.95 (general population). The effect size discriminating between patients and controls is d = 0.83 for the total score, compared to only 0.50 obtained with the two-item quality of life scale. The results prove that the calculation of sum scores provides useful information for clinicians who are interested in one generalising score of quality of life.