Triage in Healthcare: Process, Colors & Scales
In emergency care, time and resources are always limited. Triage is how care teams decide who needs help first. This guide explains how triage works in two very different settings: mass casualty incidents in the field, and the hospital emergency department (ED). It also covers the main scales clinicians use in each.
Triage is the process of quickly assessing patients and prioritizing care by clinical urgency rather than arrival order. In mass casualty incidents, responders use rapid sorting systems such as START, which assigns color-coded categories. In hospital emergency departments, nurses use five-level acuity scales such as the Emergency Severity Index (ESI), the most common in the U.S., or the Canadian Triage and Acuity Scale (CTAS). Triage isn't a one-time event: patients must be reassessed while they wait.
What is triage in healthcare?
Triage (pronounced tree-ahj) comes from the French verb trier, "to sort." It's the process of prioritizing patients based on how urgent their condition is, and sometimes on how likely they are to benefit from immediate care.
The goal isn't just to find the "sickest" patient. It's to identify patients whose conditions are time-critical and threaten life or limb, so they get care first.
Triage works differently in two settings:
| Mass casualty / field triage | Emergency department triage | |
|---|---|---|
| Goal | Do the most good for the most people with limited resources | Prioritize each individual patient by urgency |
| Typical tools | START (adults), JumpSTART (children), SALT | ESI (common in the U.S.), CTAS (Canada) |
| Time per patient | Under a minute | A few minutes, including vital signs and a focused history |
| Output | Color-coded category (red, yellow, green, black) | Acuity level from 1 (most urgent) to 5 (least urgent) |
How does START triage work in mass casualty incidents?
START (Simple Triage and Rapid Treatment) is the most widely used mass casualty triage method for adults in the U.S. It's designed to sort each patient in under a minute. After walking wounded are directed aside, responders assess the remaining patients using RPM: Respirations, Perfusion, and Mental status.
Responders remember the decision points with the mnemonic "RPM – 30 – 2 – Can Do."
How are START categories assigned?
- Can the patient walk? Patients who can walk to a designated area are tagged Green (Minor).
- Is the patient breathing?
- Not breathing, even after repositioning the airway: Black (Expectant/Deceased)
- Starts breathing after the airway is repositioned: Red (Immediate)
- Breathing faster than 30 breaths per minute: Red (Immediate)
- Breathing under 30 per minute: go to the perfusion check.
- Perfusion. If the radial pulse is absent or capillary refill takes longer than 2 seconds, tag Red (Immediate). Otherwise, go to the mental status check.
- Mental status. If the patient can't follow simple commands, tag Red (Immediate). If they can, tag Yellow (Delayed).
| Tag | Category | What it means |
|---|---|---|
| Red | Immediate | Life-threatening problem with airway, breathing, or circulation that needs immediate intervention |
| Yellow | Delayed | Serious injuries, but not expected to deteriorate significantly over several hours |
| Green | Minor | "Walking wounded" whose status is unlikely to deteriorate over days |
| Black | Expectant / Deceased | Not breathing after airway repositioning, or injuries unlikely to be survivable with the resources available |
What about children?
START is designed for adults. Children are usually triaged with JumpSTART, which adjusts the criteria for children's physiology, including different respiratory rate thresholds. Many systems also use SALT (Sort, Assess, Lifesaving interventions, Treatment/Transport), a mass casualty triage approach designed to apply across ages.
How does the Emergency Severity Index (ESI) work?
The Emergency Severity Index is a five-level ED triage algorithm used mainly in the United States. The Emergency Nurses Association (ENA) has owned ESI since 2019, and the current version is ESI Version 5 (2023).
ESI sorts patients using four decision points:
- Does the patient need an immediate life-saving intervention? Examples include airway support, emergency medications, or hemodynamic interventions. If yes, the patient is Level 1.
- Is this a high-risk situation, or is the patient confused, lethargic, disoriented, or in severe pain or distress? If yes, the patient is Level 2.
- How many different resources will the patient likely need? None means Level 5, one means Level 4, and two or more means Level 3.
- For likely Level 3 patients, are vital signs in the "danger zone"? If so, the nurse considers upgrading to Level 2.
What are the five ESI levels?
| ESI level | Description | Example |
|---|---|---|
| 1 — Resuscitation | Needs an immediate life-saving intervention | Cardiac arrest, severe respiratory distress, unresponsive |
| 2 — Emergent | High-risk situation, new confusion or lethargy, or severe pain or distress (often 7/10 or higher) | Chest pain suggestive of acute coronary syndrome |
| 3 — Urgent | Stable, but likely to need two or more different resources | Abdominal pain needing labs and imaging |
| 4 — Less urgent | Stable, likely to need one resource | Simple laceration needing sutures |
| 5 — Non-urgent | Stable, no resources expected | Prescription refill, suture removal |
What counts as an ESI "resource"?
ESI counts the number of different types of resources a patient will likely need, not individual tests. For example, a blood count and electrolytes together count as one resource (labs), while labs plus a chest X-ray count as two.
| Counts as a resource | Doesn't count as a resource |
|---|---|
| Labs (blood, urine), ECG, X-rays | History and physical exam |
| CT, MRI, ultrasound | Oral medications |
| IV fluids; IV, IM, or nebulized medications | Prescription refills, tetanus immunization |
| Specialty consultation | Phone call to a primary care provider |
| Simple procedure, such as laceration repair (counts as 1) | Simple wound care, crutches, splints, slings |
| Complex procedure, such as procedural sedation (counts as 2) | Saline lock |
Does ESI set target wait times?
Not in the way CTAS does. ESI defines urgency and expected resources, not formal time-to-physician targets for each level:
- Level 1 patients need immediate care.
- Level 2 patients should be placed rapidly, and ESI training commonly teaches that they shouldn't wait more than about 10 minutes.
- Levels 3 to 5 have no ESI-defined time targets. Timing depends on department policy and capacity.
How does the Canadian Triage and Acuity Scale (CTAS) work?
CTAS is the five-level triage scale used in Canadian emergency departments. It's maintained by a national committee of the Canadian Association of Emergency Physicians (CAEP) and the National Emergency Nurses Association (NENA).
CTAS assigns levels using the presenting complaint plus "modifiers" such as vital signs, pain severity, and mechanism of injury. Each level has a time-to-physician objective and a recommended reassessment interval.
| CTAS level | Time to physician assessment (objective) | Recommended nursing reassessment |
|---|---|---|
| 1 — Resuscitation | Immediate | Continuous nursing care |
| 2 — Emergent | Within 15 minutes | Every 15 minutes |
| 3 — Urgent | Within 30 minutes | Every 30 minutes |
| 4 — Less urgent | Within 60 minutes | Every 60 minutes |
| 5 — Non-urgent | Within 120 minutes | Every 120 minutes |
Worth being precise about: CTAS guidance recognizes that these times aren't always achievable when departments are crowded. That's one reason timely reassessment of waiting patients is emphasized.
What does an ED triage assessment include?
A triage nurse does a fast, structured assessment:
- Critical first look. Check for obvious airway problems, major bleeding, severe distress, or altered mental status. This is often called the "eyeball test."
- Chief complaint and focused history. Find out why the patient came in, when symptoms started, and how severe they are.
- Vital signs. Record blood pressure, heart rate, respiratory rate, oxygen saturation, temperature, and a pain score.
- Red-flag screening. Look for time-critical conditions such as stroke (for example, BE-FAST or FAST signs), acute coronary syndrome, sepsis, and major trauma.
- Nurse-initiated protocols. Where the hospital allows it, start standing orders before the physician sees the patient. Examples include an ECG for chest pain, IV access, or analgesia.
Also read: 7 Best Practices for Secure Triage Communication
Why is reassessment so important?
Triage is a snapshot, and patients can deteriorate while they wait. A patient triaged as ESI 3 or CTAS 3 can become critically ill in the waiting room.
- Reassess on a schedule. CTAS sets reassessment intervals by level, from continuous for Level 1 to every 120 minutes for Level 5. ESI departments typically set intervals in local policy.
- Re-triage when things change. New shortness of breath, falling consciousness, or worsening bleeding should prompt an immediate upgrade and escalation.
- Pay extra attention to high-risk groups, such as older adults, young children, and patients with high-risk complaints.
How does triage data support patient flow?
Charge nurses use triage levels to decide bed placement, where to focus available providers, and when to escalate staffing. During severe crowding, triage data can support decisions such as ambulance diversion.
Also read: Issues with Healthcare Staffing in the U.S.
How does communication affect triage safety?
Re-triage and escalation depend on fast, clear communication between triage nurses, charge nurses, and physicians. Structured formats help:
- SBAR (Situation, Background, Assessment, Recommendation) for escalation calls
- I-PASS for handoffs
Clear escalation rules matter too: everyone should know who to contact, when, and how.
Also read: SBAR: Proper Implementation and Best Examples
Where does HosTalky fit?
HosTalky is a healthcare communication platform for care teams. According to HosTalky, it supports role-based connection through &CareID, team announcements for urgent updates, and messaging across mobile and desktop. Triage teams can use these to share re-triage updates and escalations without relying on pagers or personal phones.
Escalate re-triage updates to the right person, fast.
Reach the right role and share urgent updates with your team in HosTalky, instead of chasing pages or personal phones.
Get HosTalkyKey Takeaways
- Field triage does the most good for the most people; ED triage prioritizes each patient by urgency.
- In START, a patient not breathing after airway repositioning is Black; one who starts breathing after repositioning is Red.
- ESI sorts by life-saving need, risk, and expected resources, and doesn't set time targets for Levels 3 to 5.
- CTAS sets time-to-physician objectives and reassessment intervals, from immediate to 120 minutes.
- Triage is a snapshot: reassess waiting patients and re-triage immediately when symptoms change.
FAQs
What is the difference between field triage and ED triage?
Field (mass casualty) triage, such as START, aims to do the most good for the most people with limited resources, using a quick color-coded sort. ED triage, such as ESI or CTAS, prioritizes each individual patient by urgency in a more controlled setting.
What does a red tag mean in START triage?
Red means "Immediate." The patient has a life-threatening problem and needs intervention right away. Reasons include breathing only after the airway is repositioned, a respiratory rate over 30, poor perfusion (no radial pulse or capillary refill over 2 seconds), or inability to follow simple commands.
What does ESI Level 3 mean?
ESI Level 3 is "Urgent." The patient is stable but is expected to need two or more different types of resources, such as labs plus imaging. If their vital signs are in the danger zone, the nurse may upgrade them to Level 2.
Do oral medications or prescriptions count as ESI resources?
No. Oral medications, prescription refills, simple wound care, splints, and crutches don't count as ESI resources. A patient needing only these is usually ESI Level 5.
How often should waiting patients be reassessed?
CTAS recommends continuous care for Level 1, then reassessment every 15 minutes for Level 2, every 30 minutes for Level 3, every 60 minutes for Level 4, and every 120 minutes for Level 5. ESI departments set reassessment intervals in local policy. Any patient with new or worsening symptoms should be reassessed immediately.
Is ESI or CTAS used more widely?
ESI is the most common ED triage system in the United States. CTAS is the standard in Canada and has been adapted in some other countries.
Disclaimer: This article is for educational purposes for healthcare professionals. It is not a triage protocol and doesn't replace formal ESI, CTAS, or mass casualty training, institutional policy, or clinical judgment.
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