Injury Severity Score (ISS)
Standardizes severity of traumatic injury based on worst injury of 6 body systems.
Each of the six body systems' injuries are given an Abbreviated Injury Scale (AIS); the most severe injury in each body system is used for the Injury Severity Score. Next, the three highest AIS scores are squared, then summed to determine a patient's Injury Severity Score (ISS), which ranges from 0-75. If a patient has an "Unsurvivable" injury in any of the body systems, they are automatically assigned a score of 75.
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 Mar;14(3):187-96. PubMed PMID: 4814394.