The Injury Severity Score (ISS) is an established medical score to assess trauma severity. It correlates with mortality, morbidity, and hospitalization time after a traumatic event. Use the calculator below to determine the score based on the Abbreviated Injury Scale (AIS) for each body region.
What is the Injury Severity Score?
The Injury Severity Score (ISS) is an anatomical scoring system that provides an overall score for patients with multiple injuries. Each injury is assigned an Abbreviated Injury Scale (AIS) score and is allocated to one of six body regions. The ISS is the sum of the squares of the highest AIS scores in the three most severely injured body regions.
How to Calculate the ISS
To perform an injury severity score calculation, medical professionals follow these specific steps:
- Identify Injuries: Every injury is identified and graded according to the AIS scale (1 for minor to 6 for unsurvivable).
- Categorize: Injuries are grouped into six regions: Head/Neck, Face, Chest, Abdomen, Extremities, and External.
- Select the Highest AIS: Only the highest AIS score from each region is used.
- The Formula: Take the three highest AIS scores from the three most severely injured regions, square each of them, and add them together.
Formula: ISS = (AIS A)² + (AIS B)² + (AIS C)²
Interpreting the Results
The ISS range is from 0 to 75. If any injury is assigned an AIS of 6 (unsurvivable), the ISS score is automatically set to 75, regardless of other injuries. This reflects the reality that a single unsurvivable injury dictates the prognosis.
- 0-8: Minor trauma
- 9-15: Moderate trauma
- 16-24: Serious/Severe trauma (Major Trauma threshold)
- 25-75: Critical/Extreme trauma
Clinical Significance
The ISS is considered the "gold standard" for trauma mortality prediction. It allows hospitals and trauma centers to compare outcomes, evaluate the quality of care, and categorize patients for research purposes. However, it does have limitations, such as only counting one injury per body region, which might underestimate severity in patients with multiple severe injuries in the same region.