Classifying Trauma Severity Based on Hospital Discharge Diagnoses: Validation of an ICD-9CM to AIS-85 Conversion Table

Abstract

This report describes the development and validation of a computerized system for converting ICD-9CM rubrics to Abbreviated Injury Scale (AIS) scores. In collaboration with the Committee on Injury Scaling of the Association for the Advancement of Automotive Medicine, AIS-85 scores were assigned to 2,062 injury-related ICD-9CM rubrics. To validate the conversion table, AIS and Injury Severity Scores (ISS), derived using the conversion, were compared with those obtained by reviewing the complete medical record for 1,120 trauma cases. Percent agreement in maximum AIS scores (MAXAIS) ranged from 48% for head/neck injuries to 74% for extremity injuries. In 68% of the cases, grouped ISS scores (one to 12; 13 to 19; 20+) were in agreement. Previous studies of the interrater reliability of AIS coding directly from the medical charts have shown that agreement in MAXAIS scores ranges, on average, between 62% for head/neck injuries to 76% for extremity injuries. Grouped ISS scores agree, on average, 75% of the time. The results show that while the computerized conversion is not perfect, it provides reasonably good information on severity that might otherwise be unavailable for large population-based research and evaluation. This paper discusses the potential applications of the conversion table with specific attention to its use in evaluating the extent of trauma care regionalization.