A scoping review of preference-based instruments for measuring carer outcomes in economic evaluations

Carer-specific preference-based instruments have been developed to capture outcomes for economic evaluations but the body of evidence has yet to be collated to guide instrument selection and identify knowledge gaps for future research. This scoping review aimed to identify carer-related, preference-based instruments and summarise and assess their performance, valuation and application. Nine databases (ASSIA, CINAHL, Cochrane, DARE, Econlit, EMBASE, iHTA, PsychINFO, Pubmed) were searched until 28^th May 2025 to identify peer-reviewed, English-language articles about the development, validation, valuation and application of preference-based, carer-related instruments. Study characteristics, instrument descriptions, psychometric properties and valuation information were extracted. The body of evidence and reporting quality were assessed using CREATE and the ISOQOL minimum standards for patient-reported outcome measures. In total, 140 included articles reported on five instruments: the ASCOT-Carer; the CarerQol; the CES; the ICECAP-CPM; and the SIDECAR. All carer-specific, preference-based instruments have rigorously developed scoring algorithms, albeit for differing numbers of countries. All of the instruments, except the ICECAP-CPM, have some evidence of psychometric validity in varied populations, though information on responsiveness is limited. Broadly, the CarerQol, the longest established instrument, is the most widely validated, followed by the ASCOT-Carer and CES. The SIDECAR and ICECAP-CPM require further testing. The CarerQol has the most evidence for use in carers of children, the ASCOT-Carer for adult social care settings, the CarerQoL and CES for the palliative care setting, and the ASCOT-Carer, CarerQoL, and CES for mental illness, rheumatoid arthritis, long-term care, and dementia. The CarerQol, CES and ASCOT-Carer represent the most widely used instruments for measuring carer-related outcomes in economic evaluations. The review findings assist with selecting instruments for studies alongside research objectives, population and settings. Future research should explore the responsiveness of these instruments, validate them in different countries and carer populations, and develop country-specific scoring algorithms.