Trauma scoring system
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Trauma Scoring Systems
Trauma scoring systems provide a standardized, reproducible way to quantify injury severity, guide triage, benchmark outcomes, and support research. They are broadly divided into anatomic, physiologic, and combined systems.
1. Anatomic Scoring Systems
Abbreviated Injury Scale (AIS)
First described in 1971, the AIS is the most widely used anatomic injury classification system. Each injury is coded with a 6-digit taxonomy that encodes:
- Body region (first digit)
- Type of anatomic structure
- Specific anatomic detail
A 7th digit (post-dot / severity code) rates the potential risk of death:
| Post-dot Code | Severity |
|---|---|
| 1 | Minimal |
| 2 | Moderate |
| 3 | Serious |
| 4 | Severe |
| 5 | Critical (survival uncertain) |
| 6 | Fatal |
AIS Body Regions (First Digit):
| Digit | Region |
|---|---|
| 1 | Head |
| 2 | Face |
| 3 | Neck |
| 4 | Thorax |
| 5 | Abdomen |
| 6 | Spine |
| 7 | Upper extremity |
| 8 | Lower extremity |
| 9 | Unspecified |
(Sabiston Textbook of Surgery, 14th ed., p. 652)
Injury Severity Score (ISS)
Introduced by Baker et al. in 1974, the ISS is built on the AIS. It is calculated by:
ISS = A² + B² + C² where A, B, C are the highest AIS severity codes from the three most severely injured body regions (one score per region).
- Range: 1 to 75
- If any single injury scores AIS = 6, ISS is automatically 75
- ISS >15 is associated with ~10% mortality in adults
- In children, ISS >25 is needed to predict mortality (most paediatric trauma is isolated head or extremity injury)
Severity groupings:
| ISS | Category |
|---|---|
| <9 | Minor |
| 9-14 | Moderate |
| 16-25 | Serious |
| >25 | Severe |
Limitation: Only the highest AIS in each body region is used, so multiple severe injuries within one region are underweighted.
(Sabiston, p. 652; Rockwood & Green 10th ed., p. 653)
New Injury Severity Score (NISS)
The NISS sums the squares of the three most severe injuries regardless of body region. This corrects the ISS limitation of capping at one score per region. The NISS has been shown to be more predictive of hospital resource use, complications, and mortality - particularly in penetrating injury.
AAST Organ Injury Scale (OIS)
Incorporated into modern AIS versions, the OIS assigns graded severity (I-V or VI) for specific organs. For example, lung injury grades are linked to specific AIS and ICD codes. It has been validated with the National Trauma Data Bank (NTDB).
Trauma Mortality Prediction Model (TMPM)
A more recent anatomic model based on ICD coding, providing improved mortality prediction over ISS using more standardized coding systems.
2. Physiologic Scoring Systems
These reflect the patient's post-injury physiologic state in real time, which is useful at the bedside for triage and decision-making.
Glasgow Coma Scale (GCS)
Scores 3-15, composed of three components:
| Component | Assessment |
|---|---|
| Eye Opening (E) | Spontaneous / to voice / to pain / none |
| Verbal Response (V) | Oriented / confused / words / sounds / none |
| Motor Response (M) | Obeys / localises / withdraws / flexion / extension / none |
The motor component provides the greatest statistical power for predicting survival after traumatic brain injury (TBI).
Revised Trauma Score (RTS)
The RTS incorporates coded values of three parameters:
| Parameter | Value | Coded Score |
|---|---|---|
| GCS | 13-15 | 4 |
| 9-12 | 3 | |
| 6-8 | 2 | |
| 4-5 | 1 | |
| 3 | 0 | |
| SBP (mmHg) | >89 | 4 |
| 76-89 | 3 | |
| 50-75 | 2 | |
| 1-49 | 1 | |
| 0 | 0 | |
| RR (breaths/min) | 10-29 | 4 |
| >29 | 3 | |
| 6-9 | 2 | |
| 1-5 | 1 | |
| 0 | 0 |
Total RTS: 0-12
(Sabiston, p. 653)
New Trauma Score (NTS)
An update to the RTS, the NTS uses:
- Actual GCS score (not coded)
- Coded SBP
- Pulse oximetry (SpO2) instead of respiratory rate (easier to measure and more objective)
| SpO2 | Coded Score |
|---|---|
| ≥94% | 4 |
| 80-93% | 3 |
| 60-79% | 2 |
| 40-59% | 1 |
| <40% | 0 |
Total NTS: 3-23
3. Combined (Anatomic + Physiologic) Systems
TRISS (Trauma and Injury Severity Score)
TRISS combines ISS, RTS, patient age, and mechanism of injury (blunt vs. penetrating) to calculate a probability of survival (Ps). It is widely used for quality benchmarking to compare observed vs. expected mortality across trauma centers.
4. Trimodal Distribution of Trauma Mortality
Trauma deaths classically follow a trimodal distribution:
| Peak | Timing | Cause |
|---|---|---|
| Immediate | At scene / in transit | Airway loss, devastating brain injury, high spinal cord injury, major vessel rupture |
| Early | Hours post-injury | TBI (salvageable), haemothorax, pneumothorax, solid organ injury, fracture bleeding |
| Late | Days to weeks | Sepsis, multiple organ dysfunction syndrome (MODS) |
(Rockwood & Green, p. 3027)
5. Summary Comparison
| System | Type | Parameters | Range | Primary Use |
|---|---|---|---|---|
| AIS | Anatomic | Per-injury severity | 1-6 | Injury classification |
| ISS | Anatomic | AIS of 3 regions | 1-75 | Overall severity, research |
| NISS | Anatomic | Any 3 worst AIS | 1-75 | Better for penetrating/multiple same-region |
| GCS | Physiologic | Eye, verbal, motor | 3-15 | Neurological status, TBI |
| RTS | Physiologic | GCS + SBP + RR | 0-12 | Prehospital triage |
| NTS | Physiologic | GCS + SBP + SpO2 | 3-23 | Updated triage |
| TRISS | Combined | ISS + RTS + age + mechanism | Ps (%) | Outcome benchmarking |
Key clinical pearls:
- ISS >15 predicts mortality in adults; >25 in children
- AIS = 6 in any single injury immediately sets ISS = 75
- The NISS outperforms ISS in penetrating trauma and multiple injuries within one body region
- The motor component of GCS is the strongest single predictor of TBI outcome
- RTS coded values are used at triage; TRISS requires full anatomic data (post-resuscitation)
Sources: Sabiston Textbook of Surgery, 14th ed.; Rockwood and Green's Fractures in Adults, 10th ed. (2025); Bailey and Love's Short Practice of Surgery, 28th ed.
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