The review, led by Jingxiang Pan, Chenxinan Ma, Sibo Liu, Marcus Eng Hock Ong, and Fahad Javaid Siddiqui, followed the Arksey and O’Malley scoping review framework and adhered to the PRISMA-ScR reporting checklist, the accepted standard for transparent reporting of scoping reviews. The researchers systematically searched five major bibliographic databases: PubMed, Embase, Web of Science, Scopus, and CINAHL. Their search strategy combined Boolean operators with terms covering emergency departments, overcrowding, and measurement tools, a deliberately broad approach designed to capture every instrument that has ever been proposed or tested for quantifying crowding. After removing duplicates, the team screened 1,974 papers. From that pool, 87 studies met the inclusion criteria, spanning the years 2003 to 2025, with the majority conducted in the United States, a geographic skew that itself says something important about where crowding research has been concentrated and where the evidence gaps remain.

The headline finding is that twelve distinct multidimensional measurement tools have been developed and studied over the past two decades. The list reads like an alphabet soup of emergency medicine acronyms: NEDOCS, the National Emergency Department Overcrowding Scale; PEDOCS, its pediatric counterpart; CEDOCS, designed for community hospitals; EDWIN, the Emergency Department Work Index; the occupancy rate; SONET, the Severely Overcrowded, Overcrowded, and Not Overcrowded Estimation Tool; ICMED, the International Crowding Measure in Emergency Departments; READI, the Real-time Emergency Analysis of Demand Indicators; mSEAL, a modified version of the Skåne Emergency Department Assessment of patient Load; and three further instruments, the ED workload rate, the ED work score, and the Emergency Department Crowding Scale. Each of these tools attempts to compress a chaotic, multidimensional operational reality into a number that administrators and clinicians can act upon.

The technical logic behind these instruments varies considerably, and understanding that variation is central to the review’s contribution. NEDOCS, the most widely recognized of the family, computes a composite score from inputs such as the total number of patients in the department, the longest waiting time for a bed, the number of patients waiting to be seen, the longest time since arrival for waiting patients, and the number of admitted patients holding beds in the department. The resulting score places the department on a categorical ladder from not busy to catastrophically overcrowded. EDWIN, by contrast, takes a ratio-based approach, weighing the number of patients being treated and waiting against the number of physicians on duty and the number of treatment beds, effectively capturing the relationship between demand and staffing capacity in real time. The occupancy rate is the simplest of all: the proportion of occupied treatment spaces relative to total capacity. Its elegance lies in its ease of calculation, but that simplicity is also its weakness, because a department can technically have empty beds while still being functionally gridlocked by boarding patients who cannot be moved upstairs.

Why does multidimensionality matter so much? Because crowding is not a single phenomenon but an emergent property of an entire hospital system. Input throughput describes the arrival of patients; throughput describes their movement through triage, assessment, and treatment; and output describes their discharge or admission to inpatient wards. A department can be crushed at any or all of these stages. A tool that only counts patients in the waiting room will miss the boarding crisis downstream; a tool that only tracks bed occupancy will miss the staffing shortfall that slows every consultation. The multidimensional tools reviewed here attempt to capture several of these dimensions simultaneously, which is precisely why they require more data infrastructure and why their validation is harder. The review found that the most frequently used and most extensively validated instruments were NEDOCS, EDWIN, and the occupancy rate, meaning that a substantial share of the twelve tools have been proposed or trialed but never subjected to rigorous, repeated validation across different settings.

That validation gap carries real clinical and operational consequences. If a hospital administrator in Singapore, Lagos, or rural Ohio wants to know whether their department is dangerously crowded, the answer depends heavily on which tool they choose, and the tools were largely developed in specific contexts with specific assumptions. NEDOCS thresholds, for example, were calibrated in large American tertiary centers, and there is no guarantee that a score of 140 means the same thing in a 30-bed community department as it does in a 300-bed urban trauma center. PEDOCS addresses the pediatric population, where acuity mix and flow dynamics differ from adult medicine. CEDOCS attempts to adapt measurement to community hospital realities, where resources and patient volumes differ again. The review’s authors emphasize that no single tool is universally superior; instead, suitability depends on the alignment between a tool’s data requirements, its underlying assumptions, and the operational realities of the institution deploying it.

The methodological rigor of the review itself deserves attention. The team pre-registered the study on the Open Science Framework, a step that guards against selective reporting and outcome switching. Data extraction focused specifically on each tool’s strengths, weaknesses, and contextual applicability rather than simply cataloging their existence. Study selection was documented with a PRISMA flow diagram, and the extracted data were synthesized narratively, with descriptive visualizations generated in the R statistical environment. Preliminary findings were presented at the Society for Emergency Medicine Singapore Annual Scientific Meeting in February 2025, allowing the work to be scrutinized by the emergency medicine community before formal publication. The article is published open access under a Creative Commons license, meaning the full synthesis is freely available to the hospital administrators and policymakers who most need it.

What emerges from the synthesis is a field at an inflection point. The review identifies persistent obstacles: the absence of a standardized, internationally agreed definition of overcrowding; heavy reliance on tools developed and validated in high-income, particularly American, settings; and the practical burden of data collection, since several instruments require real-time feeds from electronic health records that many hospitals, especially in low- and middle-income countries, cannot easily provide. The authors call for standardized definitions and for flexible, adaptable tools capable of addressing the diverse operational landscapes of emergency departments globally. That adaptability requirement is technically demanding: a tool must be simple enough to compute continuously without manual data entry, sensitive enough to detect meaningful changes in crowding state, and calibrated to thresholds that actually predict the adverse outcomes, such as mortality, treatment delay, and ambulance diversion, that make crowding dangerous in the first place.

The stakes of getting this right extend well beyond hospital walls. Overcrowding is frequently described as a symptom of system-wide failure rather than an emergency department problem per se, because its root causes, inpatient bed shortages, limited primary care access, and aging populations with complex needs, lie upstream and downstream of the department itself. But you cannot manage what you cannot measure, and the review makes clear that the measurement science is still maturing. As health systems worldwide grapple with surging emergency demand, the choice of a crowding metric will shape how resources are allocated, how crises are detected, and how interventions are evaluated. This scoping review provides the most comprehensive map yet of that decision space, and its central message is pragmatic: institutions should select tools that match their needs and context, while the research community works toward the standardized, adaptable instruments that global emergency care still lacks.

Subject of Research: Measurement tools for emergency department overcrowding

Article Title: Multidimensional emergency department overcrowding measurement tools: a scoping review

Article References: Pan, J., Ma, C., Liu, S., Ong, M. E. H., & Siddiqui, F. J. (2026). Multidimensional emergency department overcrowding measurement tools: a scoping review. BMC Health Services Research. https://doi.org/10.1186/s12913-026-15707-4

Image Credits: AI Generated

DOI: 10.1186/s12913-026-15707-4

Keywords: emergency department, overcrowding, NEDOCS, EDWIN, occupancy rate, scoping review, patient flow, crowding metrics, health services research, hospital capacity, validation, PRISMA

The study compared records of patient deaths within 28 days of emergency department attendance with information on how full the department was on the day each patient was seen. Occupancy was calculated in a straightforward way: by dividing the number of patients being treated by the number of available treatment spaces such as cubicles. A department with 50 cubicles and 50 patients operates at 100 per cent occupancy; with 40 patients it sits at 80 per cent, and with 60 patients it is at 120 per cent. By this measure, the departments in the study were operating at an average of 175 per cent occupancy, meaning that on a typical day many patients were being treated in spaces never designed for clinical care.

Analysis of the data showed that for every ten per cent increase in occupancy, the risk of dying from any cause within 28 days rose by one per cent. When the researchers extrapolated this relationship across the United Kingdom, they estimated that emergency department crowding could have contributed to 554 deaths a week during the study period, compared with a hypothetical situation in which every department had one space for every patient. Because the study covered the majority but not all of UK emergency departments and was, as the authors acknowledge, relatively small in statistical terms, the plausible range of excess deaths is wide: anywhere between 33 and 1,083 per week. Even at the lowest end of that range, the researchers note, the figures track similar estimates of harm from long waits and crowding published in earlier work.

The research team also examined the impact of so-called corridor care, in which patients receive treatment in non-standard clinical spaces such as corridors, waiting rooms or other areas not equipped for emergency medicine. Corridor care was likewise linked to an increase in the risk of death, broadly in line with the risk associated with the occupancy rate itself. This parallel finding matters for practical reasons: while corridor care is a visible symptom of a department in crisis, it is harder to quantify consistently across hospitals. Occupancy, by contrast, is a simple number that most departments already record, which makes it a far more usable early-warning indicator for hospital managers and health systems trying to gauge when conditions have become dangerous.

Dr McHenry framed the findings against a backdrop of deteriorating emergency care internationally. Emergency department overcrowding, he noted, is an increasing public health concern, with existing evidence showing that long delays increase patient mortality and that crowding is also associated with poor experiences for both patients and staff. He argued that traditional measures of emergency department crowding were developed at a time when the problem was far less severe, and that these older metrics are simply not sufficient to describe the crisis that currently exists in emergency care. The new study, he suggested, provides the direct evidence linking crowding itself, rather than waiting times alone, to patient deaths.

The scale of the study is one of its principal strengths. Data were collected with the help of hundreds of collaborators across 139 emergency departments, giving the researchers what they describe as a detailed and accurate view of how crowding and corridor care affect patients across a whole health system rather than at a handful of sites. Although the study was based on UK hospitals, the researchers argue that given the levels of overcrowding now reported in hospitals around the world, the relationship they observed is likely to hold in many other countries, even allowing for regional differences in how emergency care is organised and delivered.

To translate the findings into practice, the team has built an online risk calculator that allows emergency department staff to estimate the risks to patients when their department is operating beyond capacity. The tool is intended to give clinicians and managers a concrete, quantitative sense of how the conditions on a given day may be affecting outcomes, rather than relying on anecdote or intuition. The researchers say they are already engaging with governments to ensure the research feeds into health service policy, and that the next step is to identify solutions that work in tackling emergency department crowding at its sources.

Independent commentary from the European Society for Emergency Medicine underlined the wider systemic picture. Dr Felix Lorang, a member of the EUSEM abstract selection committee and head of the emergency department at Klinikum Lippe in North Rhine-Westphalia, Germany, who was not involved in the research, observed that around the world the need for emergency care is growing while infrastructure fails to keep pace. Many departments, he said, are operating far beyond capacity, and the phenomenon known as exit block, in which patients are stuck in the emergency department because no inpatient ward beds are available, places an even greater burden on staff. That, in turn, makes it harder for doctors and nurses to deliver the treatment patients need, or even the minimum treatment required to prevent further harm.

Dr Lorang described the research as making it unmistakably clear to patients, medical professionals and hospital managers alike that overcrowding and corridor care mean many emergency patients will not survive. He argued that understaffed and inadequately resourced emergency departments are, in themselves, an independent and dangerous health risk, and that the results are especially critical for governments, politicians and health services because saving lives in emergency care is achievable. The routes he identified are structural rather than clinical: preventing overcrowding through sufficient staffing, and through emergency departments that are adequately planned and equipped for the demand they actually face.

The study’s implications extend well beyond the United Kingdom. Emergency departments in many countries routinely operate above their designed capacity, and the mechanism the research points to, in which the sheer density of patients in a department erodes the safety margin for every individual within it, is not specific to any one health system. As an observational study, the research establishes a strong association rather than a definitive causal chain, and the authors themselves call for further studies to confirm the findings and to arrive at a more precise estimate of the harms from crowding. Even so, the combination of scale, geographic reach and a dose-response pattern, in which risk rises steadily with each increment of occupancy, gives the result unusual weight. If the estimate of hundreds of excess deaths a week is even broadly correct, emergency department crowding ranks among the most consequential and most preventable patient safety problems in modern health care, and the one per cent figure offers policymakers a simple, sobering arithmetic: every increment of relief delivered to a crowded department translates directly into lives that may be saved.

Subject of Research: The association between emergency department overcrowding, corridor care and increased patient mortality

Article Title: Study shows how risk of death rises with rate of overcrowding and corridor care in hospital emergency department

Article References: Study shows how risk of death rises with rate of overcrowding and corridor care in hospital emergency department. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: emergency medicine, hospital overcrowding, corridor care, patient mortality, occupancy rate, emergency departments, observational study, patient safety, exit block, health policy, European Emergency Medicine Congress, risk calculator