The Feasibility and Validity of Preference-Based Quality of Life Measures With Informal Carers: A Think-Aloud Study

Objectives: A range of preference-based quality of life (QoL) measures have been proposed for use with informal carers. Qualitative evaluation of validity and feasibility of the measures is an important step in understanding whether measures will work as intended. At present, little is known about the performance of different types of preference-based QoL measures with informal carers. The objective of this study was to qualitatively assess the feasibility, content validity (including face validity), and acceptability of 5 QoL measures (the Carer Experience Scale, CarerQoL-7D, ASCOT-C, ICECAP-A, and EQ-5D-5L) with informal carers. Methods: A total of 24 "think-aloud" interviews were conducted with a cross-section of carers of adults in the United Kingdom. This think-aloud process was followed by semistructured discussion to probe issues of validity and feasibility in more detail. The interview data were transcribed, coded to identify the frequency of errors in completing the QoL measures and thematically analyzed to study the validity, feasibility, and acceptability of the measures. Results: Few errors (3%-7% per item) were identified in completing each of the measures with little distinct pattern. Most participants found the measures to be concise, clear, and relevant. Challenges included relevance, context, time period, missing items, multiple questions, and response options. Informal carers generally expressed a preference for using a care-related QoL measure. Conclusions: Existing preference-based QoL measures have encouraging validity and feasibility within a mixed sample of informal carers, with minor challenges raised. These challenges ought to be considered, alongside the decision context, when administering QoL measures in this context.