Using generic preference-based measures (GPBMs) to capture informal carer health-related quality-of-life outcomes provides consistency across economic evaluations and facilitates combining patient and carer quality-adjusted life-years. This study assesses the psychometric performance of the 5-level EQ-5D (EQ-5D-5L) and Assessment of Quality of Life 8-Dimension (AQoL-8D) and how they conceptually relate to carer-related measures among Australian informal carers.
This was a secondary analysis of an online survey (n = 500 informal carers) containing carer-related measures (Adult Social Care Outcomes Toolkit for Carers [ASCOT-Carer], Care-Related Quality-of-Life [CarerQol], Carer Experience Scale [CES]) and GPBMs (EQ-5D-5L and AQoL-8D). Descriptive analysis, ceiling effects, convergent and known-group validity, and test-retest reliability were assessed. Exploratory factor analysis was conducted exploring the conceptual overlap between the GPBMs and carer-related measures.
Completion rates for the GPBMs were above 94%, with no ceiling effects. Test-retest reliability (only available for the EQ-5D-5L) revealed good agreement (intraclass correlation = 0.825), with moderate (usual activities, pain/discomfort, and anxiety/depression) to substantial (mobility and self-care) agreement on domains. Both GPBMs were moderately correlated with carer-specific measures and discriminated groups based on hours of care, tasks, number of care recipient diagnoses, number cared for, sharing a household, and duration of care. Exploratory factor analysis identified some overlap (predominantly health-related concepts) between carer-related measures and the GPBMs.
The EQ-5D-5L and AQoL-8D are acceptable for use in informal carers, with the choice of instrument dependent on the constructs intended to be measured. The inclusion of both GPBMs and carer-related measures during outcome assessment may still be warranted to understand carer well-being and burden.