Background: The Abbreviated Injury Scale (AIS), developed by the Association for the Advancement of Automotive Medicine is the most widely used anatomic injury severity scale in the world (Association for the Advancement of Automotive Medicine. The Abbreviated Injury Scale; 1985 and 1990 revisions. Des Plaines, IL: Association for the Advancement of Automotive Medicine). However, different user groups have modified the AIS system to fit their needs, and these modifications prevent ready comparison and trending of data collected in these systems in the United States and throughout the world. The United States currently has five AIS-based severity systems and two AIS-based impairment systems in use, with additional revisions forthcoming. Other modified AIS systems are known to be in use in the United Kingdom and Japan. The data collected in these systems cannot be accurately combined or compared without re-coding or the use of complex "mapping" methodologies. Furthermore, the expanding use of data linked from multiple databases to answer complex medical, engineering, or policy issues emphasizes the need for coordination between severity and other injury systems. Linkage of state-wide motor vehicle crash data with data from hospital injury classification systems, mortality files, trauma registry, and national crash databases brings into immediate focus the lack of well defined relationships between the severity coding systems and these other widely used injury systems (Mango N, Garthe E. SAE Congress, February, 1998; Johnson, S, Walker, J. NHTSA Technical Report. DOT HS 808 338, Washington, DC: NHTSA; January, 1996). With the expanding use of linked data in state and national policy decisions, it is vital that consistent standards for injury descriptions, severities, and impairments be available for clinical, engineering, and policy users.
Methods: This paper compares five anatomic severity systems and two impairment systems in terms of purpose, code structure, and use and discusses the reasons for the differences between these systems. With global "harmonization" encouraging greater sharing of international data, the paper also presents the relationship of the severity and impairment systems to US morbidity and reimbursement and worldwide mortality classification systems.
Results: To resolve compatibility issues resulting from multiple injury systems, the authors propose that a "unified" system for global use be developed, configured by inputs from major "data owners," users, and analysts. The proposed unified system has six key attributes: backward compatibility with historical data through "maps" so no data are lost; "scalability" to allow a simple level of use for developing countries, a more complex level for crash research and a detailed level for clinical hospital use, all with data compatibility; the ability to satisfy the needs of the engineering community for injury location information and aspect, and also the clinical requirement for precise injury description; inherent integration with whole body severity scores to permit easy computation; compatibility with other injury data systems such as mortality, morbidity, and reimbursement systems; and a mechanism and process to maintain and upgrade the system into the 21st century.
Conclusion: The authors believe that a "unified" injury system is a necessary and crucial advance from the currently fragmented injury system situation. Unified data can provide a pool of consistent international data to support a variety of important research and prevention and treatment efforts and is essential to satisfy the global needs of the medical and engineering communities.