Measures of Crowding in the Emergency Department: A Systematic Review

Authors

  • Ula Hwang MD, MPH,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Melissa L. McCarthy MS, ScD,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Dominik Aronsky MD, PhD,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Brent Asplin MD, MPH,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Peter W. Crane MD, MBA,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Catherine K. Craven MLS, MA,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Stephen K. Epstein MD, MPP,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Christopher Fee MD,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Daniel A. Handel MD, MPH,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Jesse M. Pines MD, MBA, MSCE,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Niels K. Rathlev MD,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Robert W. Schafermeyer MD,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Frank L. Zwemer, Jr. MD,

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • Steven L. Bernstein MD

    1. From the Department of Emergency Medicine, Mount Sinai School of Medicine (UH), New York, NY; the Geriatrics Research, Education and Clinical Center, James J. Peters Veterans Affairs Medical Center (UH), Bronx, NY; the Department of Emergency Medicine (MLM), William H. Welch Medical Library (CKC), Johns Hopkins University of School of Medicine (MLM), Baltimore, MD; the Department of Biomedical Informatics & Emergency Medicine, Vanderbilt University Medical Center (DA), Nashville, TN; the Department of Emergency Medicine, Mayo Clinic (BA), Rochester, MN; the Department of Emergency Medicine, University of Rochester (PWC), Rochester, NY; the Department of Emergency Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center (SKE), Boston, MA; the Department of Emergency Medicine, University of California (CF), San Francisco, CA; the Department of Emergency Medicine, Oregon Health & Science University (DAH), Portland, OR; the Departments of Emergency Medicine and Health Policy, George Washington University Medical Center (JMP), Washington, DC; the Department of Emergency Medicine, Baystate Medical Center (NKR), Springfield, MA; the Department of Emergency Medicine, Carolinas Medical Center (RWS), Charlotte, NC; the Department of Emergency Medicine, McGuire VA Medical Center, Virginia Commonwealth University (FLZ), Richmond, VA; and the Department of Emergency Medicine, Yale University School of Medicine (SLB), New Haven, CT.
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  • This paper was prepared as part of a 2008–2009 objective established for the Society for Academic Emergency Medicine (SAEM) Emergency Department Crowding Task Force by the SAEM Board of Directors. No authors have any financial conflicts of interest with the preparation of the manuscript.

  • Supervising Editor: Lawrence M. Lewis, MD.

Address for correspondence and reprints: Ula Hwang, MD, MPH; e-mail: ula.hwang@mountsinai.org.

Abstract

ACADEMIC EMERGENCY MEDICINE 2011; 18:527–538 © 2011 by the Society for Academic Emergency Medicine

Abstract

Objectives:  Despite consensus regarding the conceptual foundation of crowding, and increasing research on factors and outcomes associated with crowding, there is no criterion standard measure of crowding. The objective was to conduct a systematic review of crowding measures and compare them in conceptual foundation and validity.

Methods:  This was a systematic, comprehensive review of four medical and health care citation databases to identify studies related to crowding in the emergency department (ED). Publications that “describe the theory, development, implementation, evaluation, or any other aspect of a ‘crowding measurement/definition’ instrument (qualitative or quantitative)” were included. A ”measurement/definition” instrument is anything that assigns a value to the phenomenon of crowding in the ED. Data collected from papers meeting inclusion criteria were: study design, objective, crowding measure, and evidence of validity. All measures were categorized into five measure types (clinician opinion, input factors, throughput factors, output factors, and multidimensional scales). All measures were then indexed to six validation criteria (clinician opinion, ambulance diversion, left without being seen (LWBS), times to care, forecasting or predictions of future crowding, and other).

Results:  There were 2,660 papers identified by databases; 46 of these papers met inclusion criteria, were original research studies, and were abstracted by reviewers. A total of 71 unique crowding measures were identified. The least commonly used type of crowding measure was clinician opinion, and the most commonly used were numerical counts (number or percentage) of patients and process times associated with patient care. Many measures had moderate to good correlation with validation criteria.

Conclusions:  Time intervals and patient counts are emerging as the most promising tools for measuring flow and nonflow (i.e., crowding), respectively. Standardized definitions of time intervals (flow) and numerical counts (nonflow) will assist with validation of these metrics across multiple sites and clarify which options emerge as the metrics of choice in this “crowded” field of measures.

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