How does this Injury Severity Score (ISS) calculator work?
This is a health tool based on the internationally recognized anatomical scoring system for overall trauma severity. This injury severity score calculator helps track the most serious injuries in the six areas of the body and provides an overall score in case of patients with multiple injuries of different severities.
The score awarded by ISS is also used to define major trauma/ polytrauma in scores higher than 15. The injury severity scale is in a linear correlation with hospitalisation, mortality and morbidity.
The AIS Committee of the Association for the Advancement of Automotive Medicine (AAAM) is responsible with the creation and update of the model and there are six body regions that are being evaluated separately:
■ Head and neck – this region also includes injuries to cervical spine.
■ Face – this includes facial skeleton, nose, mouth, eyes and ears.
■ Thorax – this includes chest injuries to rib cage, thoracic spine and diaphragm.
■ Abdomen – includes abdominal organs and lumbar spine.
■ Extremities - includes pelvic skeleton injuries and sprains, fractures, dislocations.
■ External and other – include injuries such as lacerations, contusions, burns, hypothermia.
The ISS is a model aiming to bring together and reduce to a global score variable patient data, unlike other scoring systems such as the Revised Trauma Score that provide a general understanding of the overall condition of the patient. This score will then represent an accurate description of the severity of the injuries sustained.
Medical professionals who want to evaluate patients with multiple trauma and allocate the AIS codes to injuries need to be trained under a Quality Assurance programme.
Amongst the criticism received by the model is that any error in scoring the injuries by the AIS legend, is then multiplied in the overall result and the fact that it is unable to account for multiple injuries in the same body region therefore not providing any kind of weighing system in those cases. Despite this being a rapid anatomical score, it requires knowledge of the patient injuries and cannot be used as a triage tool.
Abbreviated Injury Scale
The AIS code was first introduced in 1969 and has been in permanent update ever since against survival in order to provide accurate information. Injuries are ranked from 1 to 6, 1 being minor injury and 6 being maximal, incompatible with life injury.
As an anatomic severity scoring system this is able to globally evaluate and classify an injury in any body region on a six point ordinal scale. The classification is as follows:
■ Minor (1 point);
■ Moderate (2 points);
■ Serious (3 points);
■ Severe (4 points);
■ Critical (5 points);
■ Maximal (unsurvivable) (6 points).
Each injury is assigned a score according to the Abbreviated Injury Scale. ISS is the sum of squares of the highest AIS scores awarded to the three most severely injured body regions. If there are more injuries in the same body region, the highest score is considered.
Then the 3 most severely injured regions (with the highest scores) have their scores squared and summed to provide the overall ISS score.
Values of ISS range from 0 to 75 and there are numerous combinations of scores.
However, if any region is assigned an AIS of 6 (unsurvivable injury), regardless of the squaring and sum, the overall score is automatically given as 75 because of the futility of further medical care in this type of injury that is thought to be incompatible with life.
Example multiple injury case
Let’s take in consideration the case of a patient involved in a motor accident with the following characteristics:
■ Head and neck – cerebral contusion with AIS 3 (serious).
■ Face – mandible fracture AIS 2 (moderate).
■ Thorax – rib fracture AIS 3.
■ Abdomen – liver laceration AIS 2, ruptured spleen AIS 5 (severe).
■ Extremities – no injury.
■ External and other – abrasions AIS 1 (minor).
Analyzing the injuries presented above, there are the following considerations:
- In the abdomen region since there are two types of injuries, the ruptured spleen being more severe AIS will be taken into account in the score for this region.
- The three most seriously injured regions are Abdomen (5), Head & neck (3) and Thorax (3).
- The ISS score = 52 + 32 + 32 = 25 + 9 + 9 = 43 (out of 75 possible)
References
1) Baker SP, O'Neill B, Haddon W Jr, Long WB. (1974) The injury severity score: a method for describing patients with multiple injuries and evaluating emergency care. J Trauma; 14(3):187-96.
2) Copes WS, Champion HR, Sacco WJ, Lawnick MM, Keast SL, Bain LW. (1988) The Injury Severity Score revisited. J Trauma; 28(1):69-77.
09 Aug, 2015
