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Ann Intern Med. 2017;166:707-714. doi:10.7326/M16-1927 Annals.org For author affiliations, see end of text. This article was published at Annals.org on 11 April 2017.
Firearm violence has been identified by health andlegal professionals as a critical public health prob- lem (1). Homicide is the third leading cause of death in the United States among youth aged 15 to 24 years, with more than 86% of these deaths due to firearms (2). Furthermore, firearm violence results in substantial monetary cost; for example, medical and work-loss costs of nonfatal firearm injuries treated in U.S. emer- gency departments were estimated to exceed $2.9 bil- lion in 2010 (3). Mitigating this public health issue requires novel hospital and community-based interven- tions that are focused on at-risk youth, especially those in urban communities. Urban emergency departments (EDs) have been identified as a critical access point for identifying and intervening with such youth (4). Firearm violence encompasses interpersonal, self-directed, and unintentional firearm-related incidents, but in this study we focus on interpersonal firearm violence, which we refer to simply as “firearm violence” throughout.
Although previous ED-based research (5) has iden- tified risk factors associated with firearm violence in- volvement among high-risk youth, the field of hospital and ED-based youth violence prevention programs lacks a short, clinically relevant screening tool that can be applied as part of routine clinical care in urban set- tings. Such a tool could play a key role in determining
where to focus prevention or intervention efforts. Youth identified during an ED visit, particularly violently in- jured youth, are at elevated risk for future firearm vio- lence (5) and thus would benefit most from early inter- vention, including case management and therapeutic services. Previous screening tools for youth violence (6 – 8) primarily focused on primary care settings, lack a specific focus on firearm violence, or are too lengthy for practical use in a busy ED setting. Furthermore, re- search on the construction of violence screening tools (6, 8) has been limited by small sample sizes and has not considered out-of-sample predictive power in de- vising the screen. Developing an ED/hospital-based clinical screening tool that is focused on assessing risk for future firearm violence will enable ED and hospital health systems to better focus prevention resources on patients at the highest risk.
In the current study, we seek to develop a clinical screening tool for future risk for firearm violence by examining data collected as part of a 2-year prospective study of youth aged 14 to 24 years seeking ED care. First, we used machine learning methods to determine which variables measured at the baseline of a 2-year longitudinal study were most predictive of future fire- arm violence. Second, on the basis of breadth and clin- ical feasibility, we selected 4 items from among the most predictive variables. Third, we developed cut- points and assigned point values to each level based on their relative effects, resulting in the SaFETy (Serious fighting, Friend weapon carrying, community Environ- ment, and firearm Threats) score. Finally, we examined the relationship between the SaFETy score and rates of future firearm violence within training and internal vali- dation data sets.