Protocol: A Quasi-Experimental Effectiveness and Cost-Effectiveness Evaluation of Emergency Department Violence Intervention Programmes in the United Kingdom

Introduction Hospital-based violence intervention programmes (HVIPs), based in Emergency Departments (EDs) have been proposed as a public health response to violence. These programmes address the underlying reasons why patients are exposed to violence. In addressing any underlying modifiable risks and vulnerabilities HVIPs can reduce patients’ exposure to violence and therefore subsequent unplanned attendance into ED. Methods and Analysis ED patients are eligible for inclusion in the evaluation if they are normally resident in Wales, United Kingdom (UK), aged 11 years and older. A controlled longitudinal natural experiment will be undertaken. The primary outcome is derived from the Emergency Department Dataset, routinely collected for all EDs in Wales, and is subsequent unplanned ED attendance. Case patients will be matched to control patients attending EDs without an HVIP. Analysis will derive the hazard rate for subsequent unplanned ED attendances using recurrent event analysis. The total monthly count of patients identified as attending because of violence in intervention EDs will be compared to the total count of Welsh control EDs in an interrupted time series analysis to determine whether HVIPS increase violence ascertainment. To determine whether referral, versus no referral, to the HVIP represents value for money, we will undertake a cost-effectiveness analysis from the perspective of the National Health Service. Ethics and Dissemination The approval to access and analyse data housed in the Secure Anonymised Information Linkage (SAIL) databank, an ISO 27001 certified and UK Statistics Authority accredited secure data environment, was granted by the SAIL independent Information Governance Review Panel (Ref: 1421). Findings will be presented at local, national, and international conferences and disseminated by peer-review publication. ISRCTN Registration : 41868 (12 August 2022)