Trauma systems rely on accurate injury severity scoring to describe and study trauma patient populations.
In NSW, the key criterion for including a patient record in the NSW Trauma Registry is a classification of injuries as moderate to critical, based upon an internationally recognised anatomical scoring system known as the abbreviated injury scale (AIS) and the injury severity score (ISS).10
The AIS and ISS is used by accredited staff at each hospital trauma registry to score individual patient injuries and their severity. They provide common tools for comparing and selecting patient records for inclusion in the NSW Trauma Registry.
The AIS is an anatomically-based injury severity scoring system. It classifies each injury by body region on a six point scale. The AIS is the system used to determine the ISS of the multiply injured patient.10
AIS classifications
The AIS classifies individual injuries by body region as follows:
- AIS 1 – Minor
- AIS 2 – Moderate
- AIS 3 – Serious
- AIS 4 – Severe
- AIS 5 – Critical
- AIS 6 – Maximal (currently untreatable)
The AIS version currently used in NSW is the AIS 2005 - Update 2008.11
ISS body regions
There are only six ISS body regions to which injuries can be assigned, although the AIS 2005 - Update 2008 dictionary is divided into nine anatomical chapters.11
The following may assist with assigning the body regions.
Head or neck injuries – include injury to the brain or cervical spine, skull or cervical spine fractures and asphyxia and/or suffocation.
Facial injuries – include those involving mouth, ears, nose and facial bones.
Chest injuries – include all lesions to internal organs, drowning and inhalation injury. Chest injuries also include those to the diaphragm, rib cage, and thoracic spine.
Abdominal or pelvic contents injuries – include all lesions to internal organs and lumbar spine.
Extremities or pelvic girdle injuries – include sprains, fractures, dislocations and amputations.
External and other trauma injuries – include lacerations, contusions, abrasions and burns, independent of their location on the body surface, except amputation burns that are assigned to the appropriate body region. Other traumatic events assigned to this ISS body region are: electrical injury, frostbite, hypothermia and whole body (explosion-type) injury.
ISS scoring rules
The ISS is the sum of the squares of the highest AIS code in each of the three most severely injured ISS body regions. ISS ranges from 1 to 75. If an injury is assigned an AIS of 6 (identifying a currently untreatable injury), the ISS score is automatically assigned 75.
Table 1: Example ISS calculation
| Body region | Injury | AIS code | Highest AIS | AIS² |
|---|---|---|---|---|
| Head or neck |
Cerebral contusion (NFS) Internal carotid artery transection (neck) |
140602.3 320212.4 | 4 | 16 |
| Face | Closed fractured nose | 251000.1 | 1 | |
| Chest | Rib fractures left side, ribs 3 – 4 | 450202.2 | 2 | |
| Abdomen | Retroperitoneal haematoma | 543800.2 | 2 | 4 |
| Extremities | Fractured femur (NFS) | 853000.3 | 3 | 9 |
| External | Abrasions (NFS) | 910200.1 | 1 | |
| ISS = 29 |
Injury definition
The anatomic lesion resulting from a transfer of energy (e.g. mechanical, chemical, thermal) rather than a complication or immediate sequalae from an injury.
All injuries require proper verification for injury coding (e.g. autopsy report, operation report, radiology report). Clinical diagnoses alone are not codeable, except in certain circumstances as defined by the coding rules and directives in the AIS 2005 - Update 2008 Dictionary.11
These are some things to consider when documenting injuries for injury coding.
Verified injuries
List the verified injuries and their source:
- Operation report
- Radiology
- Medical records (medical, nursing, allied health)
Terminology
- Preliminary diagnoses 'possible', '?', 'appears to be', 'rule out' are not codeable
- Rupture versus laceration will result in different AIS scoring. Remember to use the appropriate description as defined in the AIS coding manual
Specific detail
Look for specific detail of the injury:
- Size and/or depth
- Multiple, bilateral, co-existing injuries
Support materials for injury scoring with the AIS and ISS from the Association for the Advancement of Automotive Medicine website.