Evaluating quality of life outcomes following joint replacement: psychometric evaluation of a short form of the WHOQOL-Bref

Reducing participant burden is important in health research and clinical assessment. We examined the psychometric properties of the EUROHIS-QOL 8-item index, a short version of the 26-item World Health Organisation Quality of Life questionnaire (WHOQOL-Bref), in a sample of people receiving joint replacement surgery. Participants (n = 1008) completed the WHOQOL-Bref at either 6, 12, 24 or 60 months after hip or knee replacement. The factor structure, differential item functioning (DIF) and unidimensionality of the EUROHIS-QOL 8-item index were examined using exploratory and confirmatory factor analyses and Rasch analyses. Convergent validity was examined using correlations with the parent measure and other patient-reported outcome measures (Oxford scores, Western Ontario and McMaster Universities Osteoarthritis Index). Discriminant validity was assessed between groups reporting high versus low pain and function, and by joint replaced. The measure demonstrated high internal consistency (alpha = 0.86), adequate convergent (r = 0.47-0.82, p < 0.001) and discriminant validity (p < 0.001). Factor and Rasch analyses supported a unidimensional structure. However, there were also indications of multidimensionality, with support for a two-factor model focusing on general health and function, and psychosocial aspects of QOL. There was minimal evidence of DIF, with just one item evaluating energy level showing DIF for age. The EUROHIS-QOL 8-item index demonstrated adequate properties as a unidimensional scale and as a two-factor scale evaluating general health and function, and psychosocial aspects of quality of life. It is low on clinical and participant burden, showed minimal ceiling effects and showed good concurrent and discriminant validity.