A MODIFICATION OF THE INJURY SEVERITY SCORE THAT BOTH IMPROVES ACCURACY AND SIMPLIFIES SCORING

Objectives: The Injury Severity ct Score !TSS) has served as the stand ard summary measure of anatomic injury for more than 20 years. Neverth eless, the ISS has an idiosyncrasy that both impairs its predictive po wer and complicates its calculation. We present here a simple modifica tion of the ISS called the New Injury Severity Score (NISS), which sig nificantly outperforms the venerable hut dated ISS as a predictor of m ortality. Design: Retrospective calculation of NISS and comparison of MSS with prospectively calculated ISS, Materials and Methods: The NISS is defined as the sum of the squares of the Abbreviated Injury Scale scores of each of a patient's three most severe Abbreviated Injury Sca le injuries regardless of the body region in which they occur, NISS va lues were calculated for every patient in two large independent data s ets: 3,136 patients treated during a 4-year period at the American Col lege of Surgeons' Level I trauma center Albuquerque. New Mexico, and 3 ,449 patients treated during a 4-year period at the American College o f Surgeons' Level I trauma center at the Emanuel Hospital in Portland, Oregon, The pow er of NISS to predict mortality was then compared wit h previously calculated ISS values for the same patients in each of th e two data sets. Measurements and Main Results: We find that NISS is n ot only simple to calculate but more predictive of survival as well (A lbuquerque: receiver operating characteristic (ROC) ISS 0.869, ROC NIS S = 0.896, p < 0.001; Portland: ROC ISS = 0.896, ROC NISS = 0.907, p < 0.004), Moreover, NISS provides a better fit throughout its entire ra nge of prediction (Hosmer Lemeshow statistic for Albuquerque ISS = 29. 12, NISS = 8.88; Hosmer Lemeshow statistic for Portland ISS = 83.48, N ISS 19.86), Conclusion: NISS should replace ISS as the standard summar y measure of human trauma.