What affects outcomes of injuries with identical AIS severity?

Introduction The Abbreviated Injury Scale (AIS) ranks injuries on a severity scale. This presentation explores whether identical AIS scores applied to patients with isolated injuries in different body regions show significant variability in outcome. Methods Retrospective analysis of National trauma registry data (1997-2003). A comparison of mortality rates between patients with an isolated injury of an identical AIS severity in various subgroups. Subgroups were defined by body region, by age, by blunt or penetrating injury and by the presence or absence of a traumatic brain injury. Results 35,827 patients were studied. The proportion of inpatient death among patients with an isolated head injury of AIS 5 was 43%, compared with only 20% in patients with isolated abdominal or 23% in patients with isolated chest injuries of the same AIS (p<0.001). Inpatient death rate for patients with AIS severity of 5 was 31% for blunt and 44% for penetrating. Younger patients (age <50 yrs) in this AIS severity group had a 21% mortality rate compared with 49% in patients above 50 years with an identical AIS score. Conclusions AIS is the basis for calculating ISS, associated with risk of dying from injury. It is therefore important to note that identical AIS severity scores vary in outcome. This presentation shows that significant differences exist in mortality rates between patients with identical ISS from identical AIS. Variations are noted by body region injured, age and injury mechanism.