During triage in a mass casualty incident, patients are grouped into the following categories of decreasing treatment priority:

  1. Immediate: Casualties who are in need of life-saving interventions and require immediate treatment .
  2. Urgent: These casualties are unwell but with a degree of stability. They are unable to walk but have comparatively normal physiology. Typically, they will require treatment/interventions within 2-4 hrs.
  3. Delayed: Sometimes referred to as the ‘walking wounded’ these casualties are, by definition, able to ambulate to a treatment area and are deemed safe to have a treatment delay of 4 hours or more.
  4. Expectant: These casualties have such severe injuries that they are unlikely to survive with the resources available and their treatment would divert effort away from patients with a greater chance of survival; they are therefore given the lowest priority for management. Invoking the P4 category requires Gold authority (usually ministerial level) in a UK incident.

In the UK military, the prefix T is usually added to these categories; in civilian emergency services the prefix P is used.

Description T/P Colour
Immediate 1 Red
Urgent 2 Yellow
Delayed 3 Green
Expectant 4 Blue
Dead Dead Black or White

Fig 1: Triage priority categories

The ‘expectant’ category can be ethically and emotionally difficult. It is only used where resources are overwhelmed despite implementation of the normal mass casualty plan. If adequate resources become available these casualties will be treated as T1. It is important to remember the advice of the World Medical association that:

‘It is unethical for a physician to persist, at all costs, at maintaining the life of a patient beyond hope, thereby wasting to no avail scarce resources needed elsewhere’ (4).

Triage cards

As seen in Fig.1, categories also have an associated colour code. Following their assessment, casualties are given a triage card which displays this colour, allowing easy identification of those requiring the most urgent care. There are a variety of different cards available for this purpose; the SMART Tag® folded cards of the style shown below are most commonly seen at UK mass casualty incidents. These have space for basic note keeping as well as providing the visual display of the patient’s triage category.

Fig 2: An example of commonly used SMART Tag® triage cards. Available here.

Where triage cards are not available, patients may be labelled with the appropriate category number on their forehead.

It is key to note that triage is a dynamic process. As such regular re-assessment is required and if a patient’s clinical condition changes at any time, their priority category should be changed accordingly.