Abstract
IMPORTANCE: Despite evidence demonstrating that severely injured patients treated at trauma centers have improved outcomes relative to those treated at nontrauma centers, rates of undertriage (transportation of severely injured patients to nontrauma centers) remain high. While national expert panels have developed field trauma triage (FTT) guidelines to aid in the triage of injured patients, the impact of the implementation of these guidelines on existing triage patterns is unknown. OBJECTIVE: To examine the association between the 2015 update to FTT guidelines and trends in trauma triage in a mature trauma system in Ontario, Canada. DESIGN, SETTING, AND PARTICIPANTS: This retrospective, population-based cohort study was conducted from April 1, 2009, to March 31, 2020, among individuals aged at least 16 years who presented to hospital with a traumatic injury in Ontario, Canada. Statistical analysis was conducted from October 2023 to October 2025. EXPOSURE: Implementation of the 2015 update to the FTT guidelines as specified in version 2.1 of the Ontario Basic Life Support Patient Care Standards. The exposure was divided into 3 timeframes: pre-FTT (April 1, 2009, to June 30, 2014), implementation (July 1, 2014, to May 2 31, 2015), and postimplementation (June 1, 2015, to March 31, 2020). MAIN OUTCOMES AND MEASURES: Patients were categorized as undertriaged, overtriaged, or appropriately triaged based on hospital of presentation and presence of a severe injury (defined as Injury Severity Score [ISS] ≥16 or death within 24 hours of injury). Interrupted time series analysis was used to estimate temporal trends in triage rates and variations in these rates associated with the updated FTT guidelines, adjusting for differences in sociodemographic and injury characteristics. RESULTS: Of 281 268 patients with traumatic injury (mean [SD] age, 62.4 [22.5] years; 141 450 [50.3%] female; median [IQR] ISS, 4 [4-9]) included, 53 870 (19.2%) presented directly to a trauma center. Among patients who presented to a trauma center, 28 494 (52.9%) had a minor injury. Population-level rates of undertriage and overtriage were 63.5% and 12.3%, respectively. At the population level, the implementation of updated FTT guidelines was associated with a 15.2% instantaneous decrease in undertriage (rate ratio [RR], 0.85; 95% CI, 0.77-0.94). Conversely, there was no instantaneous change in overtriage (RR, 0.90; 95% CI, 0.79-1.04). During the 5 years after implementation, rates of undertriage increased by 2.4% per year (RR, 1.02; 95% CI, 1.02-1.03) while overtriage decreased by 3.8% annually (RR, 0.96; 95% CI, 0.95-0.97). Across trauma centers, the updated FTT guidelines were associated with a 14.4% instantaneous decrease in the proportion of patients with minor injuries presenting to a trauma center (RR, 0.86; 95% CI, 0.77-0.95). During 5 years after implementation, the rate at which patients with minor injuries presented directly to a trauma center remained constant (RR, 1.00; 95% CI, 0.99-1.01). CONCLUSION AND RELEVANCE: In this cohort study, the implementation of updated FTT guidelines was immediately associated with a 15% decrease in undertriage without an increase in overtriage. After the implementation of these guidelines, rates of undertriage increased by 2% each year. These findings suggest that FTT is effective in decreasing undertriage; however, ongoing monitoring is required to ensure that these benefits are maintained.