Association Between Emergency Department Undertriage or Overtriage With Timeliness of Care and Patient Outcomes - 21/02/26

Doi : 10.1016/j.annemergmed.2025.11.018

Dana R. Sax, MD, MPH ^a,^b,^⁎ , E. Margaret Warton, MPH ^b, Dustin G. Mark, MD ^a,^b, Tina J. Vitale-McDowell, RN ^c, Daniel D. DiLena, BA ^b, Adina S. Rauchwerger, MPH ^b, Mary E. Reed, DrPH ^b

^a Department of Emergency Medicine, The Permanente Medical Group, Pleasanton, CA

^b The Kaiser Permanente Division of Research, Pleasanton, CA

^c Director of Quality and Safety Improvement, Kaiser East Bay, San Rafael, CA

^∗ Corresponding Author.

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Abstract

Study objective

Assess how emergency department (ED) mistriage is associated with timeliness of ED care and patient outcomes.

Methods

This was a retrospective cohort study of ED encounters from 2016 to 2020, across 21 EDs. Using operational measures of triage accuracy, we assessed how assigned Emergency Severity Index (ESI) matched downstream intensity of care and resource use. Patients with a mismatch between ESI assignment and downstream resource use were classified as undertriaged high-acuity or overtriaged low acuity, whereas those with no mismatch were classified as true low-, mid-, or high-acuity. The primary outcome was delay in care; secondary outcomes included ED length of stay, intensive care unit admission (ICU), and short-term mortality.

Results

Among 5,315,081 adult ED encounters, mean age was 51.7 years, 2,962,827 (56%) were women, and 590,566 (11.1%), 800,966 (15.1%), 2,336,012 (44.0%), 1,137,444 (21.4%), and 450,093 (8.5%) were Asian, Black, Non-Hispanic White, Hispanic, and other, unknown or multi-race, respectively. Undertriaged high-acuity patients had higher comorbidity burdens, high-risk medication use, and recent health care use compared with true mid- and high-acuity patients. In adjusted analyses, mistriage, both under- and overtriage, was associated with small delays in care. Undertriaged high-acuity patients had an 8-minute delay in care compared with true high-acuity patients. Overtriaged low-acuity patients had a 3-minute delay in care and a 42-minute longer total ED length of stay compared with true low-acuity patients.

Conclusion

Mistriage was associated with small delays in care. Early identification of critically ill patients remains a triage priority, and the use of patient history data may help support accurate triage.

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Keywords : Triage accuracy, Mistriage, Safety outcomes, Timeliness of care

Plan

Study Design and Setting

Selection of Participants

Exposure/Intervention

Outcomes

Analysis

Results

Characteristics of Study Subjects

Undertriage Analysis: Comparing Undertriaged High-Acuity Encounters to True Mid-Acuity and True High-Acuity Encounters

Overtriage Analysis: Comparing Overtriaged Low-Acuity Patients to True Mid-Acuity and True Low-Acuity Encounters

Limitations

Discussion

	Please see page XX for the Editor’s Capsule Summary of this article.
	Supervising editor: Hemal K. Kanzaria, MD. Specific detailed information about possible conflict of interest for individual editors is available at editors .
	Author contributions: DRS, DGM, and MER conceived the study. DRS and ASR obtained research funding. DRS, MER, and TJV-M supervised the study and data collection. DRS, DGM, and TJV-M undertook recruitment of participating centers and patients and managed the data, including quality control. DDD and ASR provided administrative support. EMW provided statistical advice on study design and analyzed the data. DRS drafted the manuscript, and all authors contributed substantially to its revision. DRS takes responsibility for the paper as a whole.
	Data sharing statement: The entire deidentified data set, data dictionary and analytic code for this investigation are available on request, from the date of article publication by contacting the corresponding author.
	All authors attest to meeting the four ICMJE.org authorship criteria: (1) Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND (2) Drafting the work or revising it critically for important intellectual content; AND (3) Final approval of the version to be published; AND (4) Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
	Funding and support: By Annals’ policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org/ ). The authors report no such relationships. This study was funded by the Kaiser Permanente Northern California Community Health Fund.
	Presentation information: This research was presented at the ACEP Scientific Assembly , Salt Lake City, UT, September 7, 2025 (plenary session).