Calculator Form
Example Data Table
| Example | Age | Mechanism | RTS | ISS | Estimated Survival % |
|---|---|---|---|---|---|
| Case A | 28 | Blunt | 7.8408 | 9 | 99.42% |
| Case B | 68 | Blunt | 6.9048 | 22 | 82.53% |
| Case C | 60 | Penetrating | 4.0932 | 29 | 18.34% |
Formula Used
TRISS probability of survival: Ps = 1 / (1 + e^-b)
Logit equation: b = b0 + b1 × RTS + b2 × ISS + b3 × Age Index
Age Index: 0 for age under 55, and 1 for age 55 or older.
RTS formula: RTS = 0.9368 × GCS code + 0.7326 × SBP code + 0.2908 × RR code
ISS formula: Square and sum the top three AIS scores from different body regions. If any AIS is 6, ISS becomes 75.
TRISS Coefficients
| Coefficient | Blunt | Penetrating |
|---|---|---|
| b0 | -0.4499 | -2.5355 |
| b1 | 0.8085 | 0.9934 |
| b2 | -0.0835 | -0.0651 |
| b3 | -1.7430 | -1.1360 |
If age is under 15 years, this template applies blunt coefficients automatically.
RTS Coding Table
| Code | GCS | SBP | RR |
|---|---|---|---|
| 4 | 13–15 | ≥ 90 | 10–29 |
| 3 | 9–12 | 76–89 | > 29 |
| 2 | 6–8 | 50–75 | 6–9 |
| 1 | 4–5 | 1–49 | 1–5 |
| 0 | 3 | 0 | 0 |
How to Use This Calculator
- Enter the patient age and choose blunt or penetrating trauma.
- Pick how you want to enter RTS: directly or by using GCS, systolic blood pressure, and respiratory rate.
- Pick how you want to enter ISS: directly or by entering AIS scores for the six body regions.
- Submit the form to generate the estimated survival and mortality probabilities.
- Review the chart, derived codes, applied coefficients, and result summary.
- Use the CSV or PDF buttons to export the result for documentation or review.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates the probability of survival and mortality using trauma mechanism, age, RTS, and ISS. It is useful for structured review, audit, and comparison.
2) Why can I enter RTS directly?
Some workflows already provide a verified RTS value. Direct entry saves time and avoids repeating code conversion from GCS, systolic pressure, and respiratory rate.
3) Why can I build ISS from AIS regions?
Advanced users may know regional AIS values rather than a ready-made ISS. The form calculates ISS from the three highest regional AIS scores automatically.
4) What happens if any AIS score is 6?
The calculator sets ISS to 75 immediately. That follows the usual ISS convention for unsurvivable injury severity coding.
5) Why does age matter in TRISS?
TRISS includes an age index because increasing age is associated with worse expected outcomes. This template uses 55 years as the threshold.
6) Why does trauma mechanism matter?
Blunt and penetrating trauma use different coefficients. The same RTS and ISS values can therefore produce different survival estimates.
7) Can this replace clinical judgment?
No. It is a structured scoring tool for analysis and review. Final decisions should always follow clinical assessment, local protocol, and specialist judgment.
8) Why might another center report different results?
Different datasets, revised coefficients, local trauma populations, missing data rules, and documentation quality can all shift estimated outcomes and comparisons.