Trauma Injury Severity Score (TRISS)

Components assessed

The trauma injury severity score was created by Boyd et al. after a 1987 study aimed to integrate the evaluation of trauma in a generic procedure. The TRISS became a standardized approach for the evaluation of outcome of trauma care.

The user is asked to fill in the patient age in years and the components of the RTS and ISS:

A) Revised Trauma Score (RTS):

■ Glasgow Coma Scale (as major ER score with results from 3 to 15);

■ Systolic blood pressure (BP);

■ Respiratory rate.

B) Injury Severity Score (ISS):

■ Head and neck injury;

■ Face injury;

■ Thorax injury;

■ Abdomen injury;

■ Extremities injury;

■ External injury;

The following is the Revised trauma score survival probability table:

The Injury severity score part allows an evaluation of the existent lesions based on the anatomical region they are placed in.

The trauma score obtained varies between 0 and 75. A cut off at 15 was established as a border to major trauma/ polytrauma.

The body regions evaluated separately are:

■ Head and neck: includes injuries to cervical spine;

■ Face: includes facial skeleton, nose, mouth, eyes and ears;

■ Thorax: includes chest injuries to rib cage, thoracic spine and diaphragm;

■ Abdomen: includes abdominal organs and lumbar spine;

■ Extremities: including pelvic skeleton injuries, extremity injuries, sprains, fractures, dislocations;

■ External and other: includes injuries such as lacerations, contusions, burns or hypothermia.

Each of the injuries present is classified as minor, moderate, serious, severe, critical or maximal (un-survivable).

Beside the scores extracted from the RTS and ISS, the trauma injury severity score accounts for the patient age as an AgeIndex (as risk factors for adverse outcome), where patients below 55 are awarded 0 in the formula and patients of 55 and above are awarded 1.

By combining different trauma scores, the triage process in ER is highly standardized resulting in rapid and more accurate decision making.

TRISS formula

The survival prognosis is computed based on a logarithmic regression equation:

Survival probability = 1/(1+ e^-b)

where b = b0 + b1 x RTS + b2 x ISS + b3 x AgeIndex

Based on the table with the indices used:

The two resulting formulas for b are:

■ b_Blunt = -0.4499 + 0.8085 x RTS - 0.0835 x ISS - 1.7430 x AgeIndex

■ b_Penetrating = -2.5355 + 0.9934 x RTS - 0.0651 x ISS - 1.1360 x AgeIndex

Original source

Boyd CR, Tolson MA, Copes WS. Evaluating trauma care: the TRISS method. Trauma Score and the Injury Severity Score. J Trauma. 1987; 27(4):370-8.

Other references

1. Stewart TC, Lane PL, Stefanits T. An evaluation of patient outcomes before and after trauma center designation using Trauma and Injury Severity Score analysis. J Trauma. 1995; 39(6):1036-40.

2. Singh J, Gupta G, Garg R, Gupta A. Evaluation of trauma and prediction of outcome using TRISS method. J Emerg Trauma Shock. 2011; 4(4): 446–449.