An evaluation of ICISS methodology for determining the severity of road crash injuries using linked data

The ability to measure injury severity is important for meaningful comparison of outcomes of road crash casualties. In Western Australia, publicly reported measures of injury severity following a road crash are based on information sourced from Police crash reports. These severity ratings are determined by the attending Police Officer and categorised as: [1] fatal; [2] hospitalised; [3] minor injury; or [4] non-medical. A more robust measure is required in WA to measure the severity of road crash casualties.

Other sources for measuring the seriousness of an injury following a road crash have been used in WA. These include the ICD-based ICISS methodology, which has been applied to diagnosis data contained in WA hospital admission records. This approach has shown that serious injuries contribute to approximately 26% of WA hospital admissions by road crash casualties and are growing at a faster rate than non-serious injuries.

Additionally, the Royal Perth Hospital (RPH) Trauma Registry in WA records the Abbreviated Injury Scale (AIS) scores for all patients admitted overnight or with an AIS score of three and above. All AIS scores stored in the RPH Trauma Registry are determined by clinicians following consultation with patient. The Insurance Commission of WA (ICWA), which is the compulsory third party motor vehicle insurance provider in WA, also records AIS scores. Differently to RPH, ICWA AIS scores are determined by in-house coders working on clinical notes provided by doctors and hospitals.

Using linked hospital admissions, death registrations and road crash data in WA from 1995 to 2007, this paper will compare ICISS methodology against three other injury severity scaling methodologies: 1) police crash reports; 3) AIS recorded in the RPH Trauma Registry and; 3) AIS recorded by ICWA.