Abstract
While health services are expected to have public involvement in service (re)design, there is a dearth of evaluation of outcomes to inform policy and practice. There are major gaps in understanding why outcome evaluation is under-utilised. The aims of this interpretive descriptive study were to explore researcher participants' experiences of and/or attitudes towards evaluating health service outcomes from public involvement in health service design in high-income countries. Additionally, the aims were to explore barriers and enablers of evaluation, and reasons for the use of evaluation tools or frameworks. Semi-structured interviews (n = 13) were conducted with researchers of published studies where the public was involved in designing health services. Using framework analysis, four themes were developed that captured participants' experiences: Public involvement is hard - evaluation is harder; power, a diversity of agendas, and the invisible public; practical and methodological challenges; and genuineness and authenticity matter. Evaluation is driven by stakeholder requirements, including decision-makers, funding bodies, researchers, and academics, and evaluation tools are rarely used. The public is largely absent from the outcome evaluation agenda. There is a lack of commitment and clarity of purpose of public involvement and its evaluation. Outcome evaluation must be multi-layered and localised and reflect the purpose of public involvement, what constitutes success (and to whom), and use the most appropriate methods. Multi-level supports should include increased resources, such as funding, time, and expertise. Without improved evaluation, outcomes of investment in public involvement in health service design/redesign remain unknown.