Triage is a dynamic process used by healthcare providers to sort and prioritize patients based on the severity of their condition and the urgency of their need for medical intervention. This system ensures that the sickest or most severely injured individuals receive immediate attention, while those with less acute issues can safely wait. The entire process is a rapid assessment that determines the order in which multiple patients will receive care, particularly when resources are constrained. Triage is not a static diagnosis but an initial evaluation that can change if a patient’s condition improves or deteriorates over time.
The Fundamental Goal of Triage
The core purpose of triage is the efficient allocation of limited resources, such as specialized staff, equipment, and treatment spaces, to achieve the greatest good for the greatest number of people. This system is designed to prevent the clinical deterioration of patients who are at high risk, optimizing their chances of a positive outcome. Rapid decision-making is necessary in high-stress environments, such as a busy emergency department or during a mass casualty incident.
Triage moves beyond a simple first-come, first-served approach by systematically identifying those who cannot afford a delay in care. By categorizing patients according to the medical necessity of intervention, healthcare teams can maximize the effectiveness of their efforts.
Common Triage Scales and Their Level Counts
The question of how many levels of triage exist does not have a single, universal answer because the number varies depending on the medical setting. In hospital emergency departments across North America, the modern standard is a five-level system, which is exemplified by the Emergency Severity Index (ESI) and the Canadian Triage and Acuity Scale (CTAS). These five-level scales are considered the most effective for identifying patients needing immediate intervention and for distinguishing the relative urgency of less acute cases.
The five-level structure replaced older, less descriptive three-level and four-level models that were once common in emergency settings. Outside of the hospital, a far simpler three-level system, such as Simple Triage and Rapid Treatment (START), is still frequently used for mass casualty incidents or field disaster medicine. In these scenarios, the goal is not resource prediction but extremely rapid sorting into three broad categories: immediate, delayed, and deceased/expectant, where speed is paramount.
The Criteria for Each Severity Level
The five-level triage system stratifies patients from Level 1, requiring the most immediate and intense care, down to Level 5, representing the least urgent conditions. The assessment process involves a rapid evaluation of vital signs, the potential threat to the patient’s life or organ function, and the anticipated resources needed for their management.
Level 1 (Resuscitation)
This category is reserved for patients requiring immediate, life-saving intervention because their vital functions are unstable. Examples include cardiopulmonary arrest, severe shock, unresponsiveness, or intubation for severe respiratory failure. These patients are moved immediately to a dedicated treatment area, and a team response is initiated at the bedside.
Level 2 (Emergent)
Level 2 patients are considered high-risk individuals who face a potential threat to life, limb, or organ function, or who are exhibiting signs of confusion, lethargy, or severe pain. Although they do not require immediate life-saving procedures, their condition has the potential to rapidly deteriorate. Conditions like active chest pain, signs of stroke, altered mental status, or a significant high-risk mechanism of injury are classified here. These patients require rapid assessment and intervention, typically within minutes of arrival.
Level 3 (Urgent)
This level is assigned to patients who are stable but require two or more hospital resources for their evaluation and treatment. Resource needs include diagnostic tools such as laboratory blood work, complex imaging like CT scans, or procedures like intravenous fluid administration or complex wound repair. Patients at this level, such as those with moderate abdominal pain, mild respiratory distress, or minor fractures, can typically wait longer than Level 1 or 2 patients without a high risk of deterioration. The stability of their vital signs is a key differentiator from the higher acuity levels.
Level 4 (Less Urgent)
Patients triaged as Level 4 are stable and are only anticipated to require one hospital resource to reach a final diagnosis and disposition. Examples of resource use at this level might include a single X-ray for an ankle sprain or a simple laceration requiring basic suturing.
Level 5 (Non-Urgent)
The Level 5 category is reserved for stable patients who are not expected to require any hospital resources for their care, or perhaps only minimal resources that are not considered complex. These patients often present with chronic or minor issues that could typically be managed in an outpatient or primary care setting. Common complaints include medication refills, cold symptoms, or minor rashes.