Emergency medicine involves a density of decision-making that exceeds that of any other medical specialty. Emergency physicians face high-stakes decisions related to diagnosis, treatment, and disposition with limited information and under intense time pressure during every shift. However, the first critical decision in the emergency department (ED) is often not made by physicians, but by emergency nurses. Within minutes of a patient’s arrival, these frontline clinicians are tasked with assigning triage acuity levels that dictate the course of care for individuals and shape the operational efficiency of the entire department.^1,2 Information and time constraints are most intense at triage and variability in decision making is high.³ Such challenging circumstances are where data-driven clinical decision support (CDS) is most beneficial.

The most commonly used triage tool in the US is the Emergency Severity Index (ESI).^4,5 ESI is a five-level triage scale that relies heavily on operator intuition with an associated risk for bias and untoward variability.^3,6–9 Vital signs are the only objective data considered, with severe derangements signaling that assignment to high acuity (Level 1 or 2) should be contemplated. Differentiation between Levels 3 through 5 is determined based on anticipated ED resource utilization, with limited consideration of risk for adverse clinical outcome.⁴ Patients assigned to high or low ESI acuity have definitive care trajectories; high-acuity patients are seen within minutes of arrival⁴ and low-acuity patients are often diverted to separate workstreams for rapid treatment and disposition.² In contrast, those triaged to the mid-point (ESI Level 3) have an uncertain clinical course and experience extended wait times. Unfortunately, 50 to 70 percent of all ED patients are assigned to ESI Level 3.^10–12

Very recently, Sax et al., performed the largest study of ED triage in history. “Evaluation of the Emergency Severity Index in US Emergency Departments for the Rate of Mistriage,” published in JAMA Network Open, included 5.3 million ED encounters from 21 hospitals, all of which used ESI.¹³ Its authors utilized a granular electronic health record (EHR)-derived database and developed rigorous objective criteria to determine the accuracy of triage. They reported that one in three patients was mistriaged using ESI. Alarmingly, just 66 percent of ED patients who required life-stabilizing interventions were properly identified as high-risk (Level 1 or 2). They also found that several vulnerable populations—including those with complex medical histories, those living in poorer neighborhoods, and those who self-identified as Black—were at particularly high risk for mistriage.