IMPROVED PREDICTIONS FROM A SEVERITY CHARACTERIZATION OF TRAUMA (ASCOT) OVER TRAUMA AND INJURY SEVERITY SCORE [TRISS] - RESULTS OF AN INDEPENDENT EVALUATION

Objective: In 1986, data from 25,000 major trauma outcome study patien ts were used to relate Trauma and Injury Severity Score (TRISS) values to survival probability. The resulting norms have been widely used. M otivated by TRISS limitations. A Severity Characterization of Trauma ( ASCOT) was introduced in 1990. The objective of this study was to eval uate and compare TRISS and ASCOT probability predictions using careful ly collected and independently reviewed data not used in the developme nt of those norms. Design: This was a prospective data collection for consecutive admissions to four level I trauma centers participating in a major trauma outcome study. Materials and Methods: Data from 14,296 patients admitted to the four study sites between October 1987 throug h 1989 were used. The indices were evaluated using measures of discrim ination (disparity, sensitivity, specificity, misclassification rate, and area under the receiver-operating characteristic curve) and calibr ation [Hosmer-Lemeshow goodness-of-fit statistic CH-L)]. Measurements and Main Results: For blunt-injured adults, ASCOT has higher sensitivi ty than TRISS (69.3 vs. 64.3) and meets the criterion for model calibr ation (H-L statistic < 15.5) needed for accurate z and W scores. The T RISS does not meet the calibration criterion (H-L = 30.7). For adults with penetrating injury, ASCOT has a substantially lower H-L value tha n TRISS (20.3 vs, 138.4), but neither meets the criterion. Areas under TRISS and ASCOT ROC curves are not significantly different and exceed 0.91 for blunt-injured adults and 0.95 for adults with penetrating in jury. For pediatric patients, TRISS and ASCOT sensitivities (near 77%) and areas under receiver-operating characteristic curves (both exceed 0.96) are comparable, and both models satisfy the H-L criterion. Conc lusions: In this age of health care decisions influenced by outcome ev aluations, ASCOT's more precise description of anatomic injury and its improved calibration with actual outcomes argue for its adoption as t he standard method for outcome prediction.