Injury Severity Score (ISS)

About

• The Injury Severity Score (ISS) is an anatomical a 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 (Head, Face, Chest, Abdomen, Extremities (including Pelvis), External).
• Only the highest AIS score in each body region is used.
• The 3 most severely injured body regions have their score squared and added together to produce the ISS score.

• The ISS score takes values from 0 to 75. If an injury is assigned an AIS of 6 (unsurvivable injury), the ISS score is automatically assigned to 75.
• The ISS score is virtually the only the anatomical scoring system in use and correlates linearly with mortality, morbidity, hospital stay and other measures of severity.
• The weaknesses are that any error in AIS scoring increases the ISS error, many different injury patterns can yield the same ISS score and injuries to different body regions are not weighted.
• Also, as a full description of patient, injuries is not known prior to full investigation & operation, the ISS (along with other anatomical scoring systems) is not useful as a triage tool.
• Baker SP et al, "The Injury Severity Score: a method for describing patients with multiple injuries and evaluating emergency care", J Trauma 14:187-196;1974

The Abbreviated Injury Scale (AIS)

• This is an anatomical scoring system first introduced in 1969. Since this time it has been revised and updated against survival so that it now provides a reasonably accurate was of ranking the severity of the injury.
• The latest incarnation of the AIS score is the 1990 revision. The AIS is monitored by a scaling committee of the Association for the Advancement of Automotive Medicine.
• Injuries are ranked on a scale of 1 to 6, with 1 being minor, 5 severe and 6 an unsurvivable injury. This represents the 'threat to life' associated with an injury and is not meant to represent a comprehensive measure of severity.
• The AIS is not an injury scale, in that, the difference between AIS1 and AIS2 is not the same as that between AIS4 and AIS5.
• There are many similarities between the AIS scale and the Organ Injury Scales of the American Association for the Surgery of Trauma.