Development and Content Validation of the 10-item Well-being Instrument (WiX) for use in Economic Evaluation Studies

It’s increasingly recognized that the evaluative space of economic evaluations in health and social care needs to be broadened and instruments measuring well-being are required. A generic measure of well-being comprehensively capturing all relevant domains of well-being in the adult population is not available. The aim is to describe the development of such an instrument, the 10-item Well-being instrument (WiX), and to report the findings from a content validation study. A draft version of the instrument was based on available instruments pursuing the same aim, a comprehensive theoretical framework of the domains of well-being, and recent empirical evidence from the general population about the constituents of well-being. Content validation was conducted following COSMIN methodology and investigated relevance, comprehensiveness, and comprehensibility. In the qualitative content validation, semi-structured interviews were conducted with experts and members of the general population. During quantitative content validation, a representative sample (n = 501) from the general population completed an online survey. The qualitative validation showed the relevance and comprehensiveness of the WiX were adequate, but several changes were made to consecutive draft versions of the items and their descriptions and response levels to improve comprehensibility. The quantitative validation confirmed these findings and resulted in some additional, minor changes. A new instrument aiming to capture overall (or general) quality-of-life in terms of subjective well-being by measuring how satisfied people are on ten important domains of life in the adult general population was developed. The content validation results are encouraging, but further validation and valuation steps are necessary before the WiX can be used in (economic) evaluation studies of interventions with impacts broader than health.