Emergency Severity Index (ESI): A Triage Tool for Emergency Departments


The Emergency Severity Index (ESI) is a tool for use in emergency department (ED) triage. The ESI triage algorithm yields rapid, reproducible, and clinically relevant stratification of patients into five groups, from level 1 (most urgent) to level 5 (least urgent). The ESI provides a method for categorizing ED patients by both acuity and resource needs.

Emergency physicians Richard Wuerz and David Eitel developed the original ESI concept in 1998. After pilot testing of the ESI yielded promising results, they brought together a number of emergency professionals interested in triage and the further refinement of the algorithm. The ESI Triage Group included emergency nursing and medical clinicians, managers, educators, and researchers. The ESI was initially implemented in two university teaching hospitals in 1999, and then refined and implemented in five additional hospitals in 2000. The tool was further refined based on feedback from the seven sites. Many research studies have been conducted to evaluate the reliability, validity, and ease of use of the ESI.

One of the ESI Triage Group's primary goals was to publish a handbook to assist emergency nurses and physicians with implementation of the ESI. The group agreed that this was crucial to preserving the reliability and validity of the tool. A draft of this handbook was in progress in 2000, when Dr. Wuerz died suddenly and unexpectedly. The remaining group members were committed to the value of ESI and carrying out Dr. Wuerz's vision for a scientifically sound tool that offers emergency departments a standardized approach to patient categorization at triage. The group completed the first edition of The Emergency Severity Index (ESI) Implementation Handbook in 2002 (published by the Emergency Nurses Association [ENA]). The group then formed The ESI Triage Research Team, LLC, and worked with the Agency for Healthcare Research and Quality, which published the second edition in 2005. This 2012 edition has been significantly updated. ESI Version 4 is presented in the current handbook. Supporting research is presented in Chapter 2. Pediatric validation research led to the addition of a new pediatrics chapter to this edition.

The handbook is intended to be a complete resource for ESI implementation. Emergency department educators, clinicians, and managers can use this practical guide to develop and conduct an ESI educational program, implement the algorithm, and design an ongoing quality improvement program. This edition of the book includes:

  • Background information on triage acuity systems in the United States.
  • A summary of ESI research.
  • An overview of triage acuity systems in the United States and research reports using ESI.
  • An overview chapter describing ESI in detail: identifying high-risk patients, predicting resources, and using vital signs.
  • The new pediatric chapter.
  • Chapters on ESI implementation and quality monitoring.
  • Chapters with practice and competency cases, including many new cases.

The handbook can be used alone or in conjunction with the training DVD, Emergency Severity Index, Version 4: Everything You Need to Know, also produced by AHRQ.

The ESI represents a major change in the way triage is practiced; implementation of the ESI requires a serious commitment from education, management, and clinical staff. Successful implementation of this system is accomplished by committing significant resources during training and implementation. A myriad of benefits may result from a successful ESI implementation: improvements in ED operations, support for research and surveillance, and a standardized metric for benchmarking.

This handbook is intended only as a guide to using the ESI system for categorizing patients at triage in ED settings. Nurses who participate in an ESI educational program are expected to be experienced triage nurses and/or to have attended a separate, comprehensive triage educational program.

This handbook is not a comprehensive triage educational program. The ESI educational materials in this handbook are best used in conjunction with a triage educational program. Triage nurses also need education in institution-specific triage policies and protocols. For example, hospitals may develop policies regarding which types of patients can be triaged to fast-track. Triage protocols may also be developed, such as giving acetaminophen for fever, or ordering ankle films for patients who meet specified criteria.

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Page last reviewed October 2014
Page originally created September 2012
Internet Citation: Emergency Severity Index (ESI): A Triage Tool for Emergency Departments. Content last reviewed October 2014. Agency for Healthcare Research and Quality, Rockville, MD. https://www.ahrq.gov/professionals/systems/hospital/esi/esipref.html
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