OBJECTIVES: This study examines convergent, known group validity, interrater reliability, and responsiveness of proxy reports of aged care residents' health-related quality of life on the EQ-5D-5L.

METHODS: The study used baseline and 12-month data from 281 residents participating in a deprescribing randomised control trial in Australia between 2014 and 2018. Interview-administered paper-based questionnaires were used for data collection, including the Mini-Mental State Examination, Modified Barthel Index, Neuropsychiatric Inventory scale, and Rockwood Frailty Index. Convergent validity, known group validity, and responsiveness were tested using Spearman Rho, Mann-Whitney, and Kruskal-Wallis tests. Interrater reliability was examined by calculating the intra-class correlation coefficient and Cohen's kappa and graphing Bland-Altman plot and bar charts.

RESULTS: Proxy reports on EQ-5D-5L were significantly associated with residents' cognitive functioning, physical functioning, neuropsychiatric behaviours, and frailty. Proxy reports on EQ-5D-5L significantly differed across clinical severity thresholds of cognitive functioning, physical functioning, neuropsychiatric behaviours, and frailty. The intra-class correlation coefficient for total utility score was moderate at baseline and 12 months. Cohen's kappa tests were significant in self-care and usual activities at baseline and 12 months. Changes in proxy reports on EQ-5D-5L over 12 months were significantly associated with changes in residents' cognitive functioning, physical functioning, neuropsychiatric behaviours, and frailty over 12 months.

CONCLUSIONS: Proxy reports on EQ-5D-5L had satisfactory convergent, known-group validity and responsiveness. Interrater reliability was moderate at the total utility score but poor at the domain level. Proxy reports on EQ-5D-5L can be an alternative in residential aged care facilities.