Sessions
Coding and
Classification
of Non-Fatal Injuries
The Future of the AIS
Thomas A. Gennarelli, M.D.
Elaine Petrucelli
Origins of Today’s AIS
The Abbreviated Injury Scale (AIS) was first conceived three decades ago as a system to define the severity of injuries throughout the body. Its original purpose was to fill a need for a standardized system for categorizing the type and severity of injuries arising from vehicular crashes. At first the intention was to map a series of anatomically defined injuries by several parameters (energy dissipation, threat to life, permanent impairment, treatment period, incidence). The original AIS of 1971 was thus defined. By 1975-76 the first injury dictionary was published. This was a list of approximately 500 injuries and severity levels ranging from 1 (least severe) to 6 (most severe). There was an attempt to expand the types of injuries beyond impact injury by the inclusion of burns. This was done because of the frequency of burns in motor vehicle crashes. By this time the AIS had been adopted as the standard for crash teams funded by the U.S. Department of Transportation, as well as many university and industry research teams in the U.S, Europe and Australia.
The Committee on Injury Scaling of the Association for the Advancement of Automotive Medicine (formerly the American Association for Automotive Medicine), the parent body of the AIS, continued to modify the AIS to remain in touch with contemporary issues. Thus, in 1980 the injury dictionary was expanded by three-fold and the descriptions of many injuries were improved. The brain injury section was updated to parallel contemporary research in head injury. By 1985 another revision of AIS was published with the incorporation of descriptors that would allow coding of penetrating injuries. This version first introduced a numeric system that assigned a unique code number to each injury to facilitate computerized use of the AIS. Both of these revisions, along with further refinement and specificity of injury descriptors (especially in the thorax and abdomen) were instituted in response to the needs of a growing wave of organized trauma care and the need for trauma centers throughout the world to communicate with one another. Finally, in 1990 another major update of AIS was presented to expand the number and sophistication of injury descriptors with an eye to differences that would be useful for impairment or non-fatal outcome determinations. In addition, the special needs of penetrating injuries and injuries to children were addressed. The numerical injury identification system was improved and guidelines for coding were presented to promote uniformity of injury coding. The 1990 AIS was updated in 1998 to clarify several issues, but this was not a major departure from AIS 1990.
Philosophical Basis for the AIS
Throughout all of the AIS revisions, there have been certain principles that have been used to guide any changes. These principles have remained as constant as feasible, given the profound changes that have occurred in injury epidemiology, the vehicular environment, and trauma care in the world over the past 30 years. Among these principles are the following concepts:
- the AIS should be a simple method to rank injuries by severity
- there should be standardization of terminology to describe injuries
- the AIS should be applicable for many causes of injuries
- the AIS should be compatible both for large and small scale data collections
- the injury descriptors are organized anatomically, not physiologically
- the AIS severity score is a single, time independent value for each injury
- the AIS considers the injury, not its consequences
- the AIS is more than a mortality or threat to life measure
- the described injury occurs to an otherwise healthy adult
- each severity score reflects a single injury being present
- the severity is described regarding its importance to the whole body
These principles have been slightly modified over the years, but only in a few circumstances in order to add clarity and definition to injury descriptors. Clearly, these principles define both the utility and the limitations of the AIS.
Because of these principles, the AIS has been defined as follows:
The AIS is an anatomically based, consensus derived, global severity scoring system that classifies each injury in every body region according to its relative importance on a 6 point ordinal scale.
Future Challenges for the AIS
It has been ten years since the AIS was last revised and plans exist for another major revision … the AIS 2000. In that interval a number of factors have occurred that influence the potential nature of the revision. These include:
- the emerging interest in the development of injury scaling in specific injury areas, either by medical sub-specialists or by road traffic investigators. Thus, there is a potential for multiple-alternative scaling systems for very special interests. Although it is well recognized that no single severity system can be used for every purpose, there is concern that the generation of increased special interest systems may detract from the overall goal of a common severity language, since these systems most probably will not relate to each other, to the AIS, or to any common system.
- the appearance of a growing disparity in the data quality available to various data collection systems. This factor causes polarization between users who require extreme specificity in injury descriptions and those whose data sources have relatively general injury descriptions. Consequently, there is a perceived need to develop two systems, one for databases that have only limited medical detail and a second where extremely detailed medical description of injuries is available.
- differences exist in the needs of users in different countries
- changes in hospital-based injury descriptors are apparent, especially during the transition from ICD9-CM to a not yet finalized ICD10-CM.
- the lack of description of the localization of injuries within the injured organ (i.e., right-left, proximal-distal, anterior-posterior, etc.)
Thus, the overall goals for the current AIS revision have had to take these concerns into account. Therefore, the general goals for the AIS 2000 revision have been defined as follows:
- define the constituency of AIS user groups
- define the users’ needs nationally and internationally
- develop an AIS system that responds to users’ needs
- respond to users’ concerns about AIS on an ongoing basis
- assure that no user group becomes disenfranchised or predominant
- continue to define the injury dictionary to account for outcome
In order to achieve these goals, the Injury Scaling Committee was recently reconstituted and its mission statement refined. The newly constructed committee, now called the International Injury Scaling Committee (IISC) will have broad, new multinational representation from many disciplines that represent the spectrum of users. This includes many medical specialties that deal with trauma care and its epidemiology, biomechanics and prevention, as well as representatives from governmental agencies and industry that deal with transport and other injury issues. Representation will be sought from organizations with interests in injury or outcome scaling in hopes of developing mutually compatible systems. The IISC will deal not only with injury severity via the AIS, but will also promote outcome sciences and the continued improvement of tools that better define the outcome of non-fatal injuries.
In planning for the 2000 revision of the AIS, the following specific tasks will be achieved:
- develop comparability with other existing or proposed injury scoring system, including, for example, the Organ Injury Scaling (American Association for the Surgery of Trauma) and the Orthopedic Trauma Association (OTA) Fracture Classification system.
- address and resolve compatibility issues with ICD10- CM
- expand the AIS pre-dot code to include locators for injury location (aspect, side)
- revise the AIS orthopedic injury descriptors to be more compatible with those of the OTA and to attempt to code increased specificity in the pre-dot code
- develop AIS codes for bilateral injuries for more precise impairment correlation
- develop rubrics that deal with common injury combinations that may affect outcome or impairment (e.g. long bone fracture with nerve injury )
- to develop a system to scale multiple injuries in a body region that may effect mortality (e.g. bilateral sub-dural hematomas)
- develop better compatibility between more or less injury detail
- continue to refine the injury descriptors so that they are capable of describing threat to life as well as impairment and functional capacity.
It is anticipated that the AIS 2000 will be the culmination of the collaborative efforts of many disciplines, organizations and nations, and that this product, like it’s predecessors, will provide a valuable research tool that will remain the gold standard for injury severity determination for years to come.