How should services for high-intensity users be organised? A scoping review of published literature with recommendations for future research and delivery of care.

Objective: High Intensity Users (HIUs) of Urgent and Emergency Care (UEC) services account for disproportionately high numbers of Emergency Department (ED) attendances, ambulance journeys and non-elective admissions. This review aimed to assess the quality and completeness of evidence for understanding the characteristics of HIUs, how best to identify and differentiate them, the effectiveness of services to support them, and to identify areas for further research. Design: Scoping review of UK-based peer-reviewed literature. Setting: Four databases (January 2010 to October 2025) - additional grey literature identified through hand searching and Google searches. Participants: Twenty-eight published articles (19 peer-reviewed papers, 9 grey literature). Main outcome measures: HIU definitions, descriptions, effectiveness of care, characteristics of successful programmes and interventions. Results: HIUs are generally defined by the frequency of UEC use rather than diagnosis or need, despite being highly heterogeneous. The national model of care adopted in England relies largely on individual Case Managers supporting small numbers of HIUs. Although most published evaluations report reductions in ED attendances and admissions, and positive impacts on individual well-being, they are generally small, uncontrolled, and short-term with poorly defined interventions and minimal evidence that they reduce overall demand on UEC services. Conclusions: Further research is needed to better characterise HIUs, drivers of their behaviour and risk factors to determine which HIUs benefit from which interventions. Services need to operate at scale using near-real time data, be integrated with health as well as social care services, and use standardised, granular definitions of HIUs to guide appropriate interventions.