This trauma injury severity score (TRISS) calculator prognosticates blunt and penetrating trauma survival based on patient age, RTS and ISS results. Below the form you can find the formulas used and an interpretation of all variables employed in this composed trauma score.
How does the trauma injury severity score (TRISS) calculator work?
This health tool estimates survival rates from blunt or penetrating trauma based on the results from two trauma scoring systems: the Revised Trauma Score (RTS) and the Injury Severity Score (ISS) and an extra variable, the patient age.
The RTS part in this TRISS calculator accounts for main vital signs and predicts patient outcome in traumatic and non traumatic incidents:
■ Glasgow coma score (GCS) – major ER score with results between 3 and 15, the highest scores being least severe;
■ Systolic blood pressure – in mmHg with the normal range below 120 mmHg and hypertension consistent values above 140 mmHg;
■ Respiratory rate – also known as ventilation rate (cycles of inspiration and expiration in a minute) with normal values in adults around 20 breaths per minute.
Revised trauma score survival probability table:
| Revised Trauma Score (RTS) | Survival probability |
| 0 | 2.70% |
| 1 | 7.10% |
| 2 | 17.20% |
| 3 | 36.10% |
| 4 | 60.50% |
| 5 | 80.70% |
| 6 | 91.90% |
| 7 | 96.90% |
| 7.84 | 98.80% |
The ISS part accounts for types of lesions in the recognized anatomical regions in order to compute a trauma score. Result range varies between 0 and 75 and a cut off at 15 signals major trauma/ polytrauma.
The body regions evaluated separately are:
■ Head and neck – also including injuries to cervical spine;
■ Face – including facial skeleton, nose, mouth, eyes and ears;
■ Thorax – including chest injuries to rib cage, thoracic spine and diaphragm;
■ Abdomen – including abdominal organs and lumbar spine;
■ Extremities – including pelvic skeleton injuries, extremity injuries, sprains, fractures, dislocations;
■ External and other – including injuries such as lacerations, contusions, burns or hypothermia.
Each of the injuries is classified as minor, moderate, serious, severe, critical or maximal–unsurvivable.
Beside the two systems presented above, TRISS takes account of patient age in an AgeIndex that is:
■ 0 – for patients below 55;
■ 1 – for patients 55 and above.
TRISS calculation
The survival prognosis is computed based on the below logarithmic regression equation and formulas:
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:
| Blunt | Penetrating | |
| b0 | -0.4499 | -2.5355 |
| b1 | 0.8085 | 0.9934 |
| b2 | -0.0835 | -0.0651 |
| b3 | -1.743 | -1.136 |
The two resulting formulas for b are:
■ bBlunt = -0.4499 + 0.8085 x RTS - 0.0835 x ISS - 1.7430 x AgeIndex
■ bPenetrating = -2.5355 + 0.9934 x RTS - 0.0651 x ISS - 1.1360 x AgeIndex
This combined trauma score allows in trauma triage processes in ER to include both anatomical and physiological measures thus resulting in higher specificity.
References
1) Boyd CR, Tolson MA, Copes WS. (1987) Evaluating trauma care: the TRISS method. Trauma Score and the Injury Severity Score. J Trauma; 27(4):370-8.
2) Llullaku SS, Hyseni N, Bytyçi CI, Rexhepi SK. (2009) Evaluation of trauma care using TRISS method: the role of adjusted misclassification rate and adjusted w-statistic. World J Emerg Surg; 4: 2.
3) Singh J, Gupta G, Garg R, Gupta A. (2011) Evaluation of trauma and prediction of outcome using TRISS method. J Emerg Trauma Shock; 4(4): 446–449.
4) Baker SP, O'Neill B, Haddon W Jr, Long WB. (1974) The injury severity score: a method for describing patients with multiple injuries and evaluating emergency care. J Trauma; 14(3):187-96.
5) Champion HR, Sacco WJ, Copes WS, Gann DS, Gennarelli TA, Flanagan ME. A revision of the Trauma Score. (1989) J Trauma; 29(5):623-9.
05 Apr, 2016