Several commonly used scoring methods rate severity of injury following MVA/MVCs (occupant or pedestrian). First introduced in1969, the Abbreviated Injury Scale (AIS) is an anatomical scoring system. It has been revised and updated against survival data and now provides a fairly accurate method of rating the severity of injury (Table 17-1). The most recent version of the AIS was published in 1990; this tool is updated/revised periodically by the Association for the Advancement of Automotive Medicine (Baker, O’Neill, Haddon, & Long, 1974).
Injuries are ranked on a scale of 1 to 6. Minor injuries are scored as 1, severe injuries are 5, and injuries incompatible with life are 6. The resulting score represents the “threat to life associated with the injury,” not a comprehensive measure of severity (Baker, O’Neill, Haddon, & Long, 1974).
In 1974, the Injury Severity Score (ISS) was created using the AIS score applied to each of six anatomic regions: head, face, chest, abdomen, extremities (includes pelvis), and external. The highest AIS score for each region is used. Only the three most severely injured body regions scores are squared and then added together to produce the ISS score (Baker, O’Neill, Haddon, & Long, 1974). An example of the ISS calculation is shown in Table 17-2.
The ISS score ranges from 0 to 75. When any injury is ranked as AIS 6 (unsurvivable injury), the ISS is automatically scored 75. The ISS score correlates linearly with mortality, morbidity, hospital stay and other measures of severity (Baker & O’Neill, 1976; Baker, O’Neill, Haddon, & Long, 1974).