TRISS – Trauma and Injury Severity Score
Estimates probability of survival for trauma patients using RTS, ISS, age, and mechanism
For use by health professionals only. This implementation uses the classic MTOS TRISS coefficients for educational and audit support purposes. It does not replace trauma team assessment, local major trauma protocols, or shared decision-making. Not for patient self-use.
Enter patient data
RTS (weighted): –
Age index (≥55 years): –
TRISS probability of survival (Ps): –
Interpretation: Not yet calculated
Enter GCS, SBP, RR, ISS, age and mechanism, then click “Calculate TRISS” to see RTS, Ps, and a broad interpretation band.
This calculator uses classic MTOS “outcome norm” coefficients: Blunt: b0 = −0.4499, b1 = 0.8085, b2 = −0.0835, b3 = −1.7430; Penetrating: b0 = −2.5355, b1 = 0.9934, b2 = −0.0651, b3 = −1.1360. Ps = 1 / (1 + e−b), where b = b0 + b1·RTS + b2·ISS + b3·AgeIndex. Local registries may use updated coefficients; always check your institutional standard.
The Trauma and Injury Severity Score (TRISS) is a combined anatomical–physiological prediction model that estimates a trauma patient’s probability of survival (Ps). It was developed in the 1980s using the Major Trauma Outcome Study (MTOS) dataset and is still widely used for benchmarking trauma care, audit, and research, rather than bedside decision-making for individual patients. Life in the Fast Lane • LITFL+1
TRISS combines:
- Revised Trauma Score (RTS) – a physiologic score based on GCS, systolic blood pressure (SBP), and respiratory rate (RR) on arrival. Life in the Fast Lane • LITFL+1
- Injury Severity Score (ISS) – an anatomical score derived from AIS-coded injuries. Wikipedia+1
- Age – dichotomised (≥55 years vs <55 years). PMC+1
- Mechanism of injury – blunt vs penetrating, each with its own regression coefficients. PMC+2www.slideshare.net+2
How TRISS is calculated
- Code the physiology (RTS)
- Convert GCS, SBP and RR into coded values from 0–4 based on ranges (e.g. GCS 13–15 → 4; SBP >89 mmHg → 4; RR 10–29 → 4). Life in the Fast Lane • LITFL+1
- Compute weighted RTS:
RTS = 0.9368 × GCSᶜ + 0.7326 × SBPᶜ + 0.2908 × RRᶜ. www.elsevier.com+1
- Get ISS from AIS-based anatomical coding (0–75). Wikipedia+1
- Define AgeIndex
- AgeIndex = 0 if age <55 years
- AgeIndex = 1 if age ≥55 years. www.slideshare.net+1
- Apply mechanism-specific logistic model
Using the classic MTOS/“outcome norms” TRISS coefficients: www.slideshare.net+1
For blunt trauma
b = −0.4499 + 0.8085·RTS − 0.0835·ISS − 1.7430·AgeIndex
For penetrating trauma
b = −2.5355 + 0.9934·RTS − 0.0651·ISS − 1.1360·AgeIndex
Then:
Probability of survival, Ps = 1 / (1 + e^(−b))
(Ps ranges from 0 – certain death – to 1 – predicted survival.)
In many implementations, paediatric patients (<15 years) use the blunt coefficients even for penetrating mechanisms. www.slideshare.net+1
Interpretation and limitations
- Higher Ps → higher predicted chance of survival (e.g. Ps 0.97 ≈ 97% survival probability).
- TRISS is excellent for system-level comparison (e.g. standardised mortality ratios), but only moderately accurate for individual patients and can drift out of calibration as trauma care improves. ScienceDirect+1
- Limitations include dependence on accurate ISS/AIS coding, difficulties with missing physiological data (e.g. intubated patients), and limited adjustment for comorbidities and frailty (especially in older adults). Medscape eMedicine+1
Clinical note: TRISS is best viewed as a benchmarking / audit tool, not a sole determinant of treatment, futility, or triage for any individual trauma patient.
