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Injury Severity Score (ISS) Calculator

What is the Injury Severity Score (ISS)?

The Injury Severity Score (ISS) is an anatomical scoring system that provides an overall score for patients with multiple injuries. It is used to assess the severity of trauma and is calculated based on the Abbreviated Injury Scale (AIS), which classifies each injury by body region on a scale of 1 to 6, with 1 being minor and 6 being unsurvivable.

Clinical Significance

The ISS is widely used in trauma care and research to:

  • Predict mortality and morbidity in trauma patients
  • Triage patients to appropriate levels of trauma care
  • Compare outcomes across different trauma centers
  • Evaluate the effectiveness of trauma care systems
  • Standardize research in trauma care

An ISS score greater than 15 is generally considered to indicate major trauma, and patients with such scores typically require treatment at a designated trauma center.

How is the ISS Calculated?

The ISS is calculated by:

  1. Dividing the body into six regions:
    • Head and Neck
    • Face
    • Chest
    • Abdomen
    • Extremities (including pelvis)
    • External
  2. Assigning an AIS score (1-6) to each injury in each body region
  3. Identifying the highest AIS score in each of the three most severely injured body regions
  4. Squaring each of these three scores
  5. Summing these squared values to obtain the ISS

The ISS ranges from 0 to 75. If any injury is assigned an AIS of 6 (unsurvivable), the ISS is automatically set to 75, which is the maximum score.

Interpretation

The ISS score can be interpreted as follows:

  • 1-8: Minor injury
  • 9-15: Moderate injury
  • 16-24: Severe injury
  • 25+: Very severe injury
  • 75: Unsurvivable injury

The mortality rate increases with higher ISS scores, with a significant increase in mortality for scores above 15.

Limitations

While the ISS is a valuable tool, it has several limitations:

  • It only considers one injury per body region, potentially underestimating the severity in patients with multiple injuries in the same region
  • It equally weights injuries in different body regions, which may not reflect their true clinical impact
  • It requires detailed knowledge of the AIS scoring system
  • It does not account for age or comorbidities, which significantly affect outcomes
  • It may not accurately predict outcomes in pediatric trauma patients

References

  1. Baker SP, O'Neill B, Haddon W Jr, Long WB. The injury severity score: a method for describing patients with multiple injuries and evaluating emergency care. J Trauma. 1974;14(3):187-196.
  2. Copes WS, Champion HR, Sacco WJ, Lawnick MM, Keast SL, Bain LW. The Injury Severity Score revisited. J Trauma. 1988;28(1):69-77.
  3. Osler T, Baker SP, Long W. A modification of the injury severity score that both improves accuracy and simplifies scoring. J Trauma. 1997;43(6):922-925.