Injury Severity Score versus New Injury Severity Score for penetrating injuries

The New Injury Severity Score (NISS) was introduced in 1997 to improve outcome prediction based on anatomical severity scoring in trauma victims. Studies on populations of blunt trauma victims indicate that the NISS, predicts better than the Injury Severity Score (ISS) mortality post-injury, which is why the NISS has been recommended as the new "gold standard" for severity scoring. However, so far the accuracy of the NISS for penetrating injuries has not been validated against the ISS.

ISS and NISS scores were collected retrospectively for 1,787 war- and landmine victims in North Iraq. All victims only had penetrating injuries. The two tests were compared for prediction of short-term mortality and post-operative complications using Receiver Operating Characteristics (ROC) analysis.

Both the ISS and the NISS predicted mortality with high accuracy (ROC area under curve 0.9). There were no significant differences between the two tests. The predictive accuracy for post-operative complications was moderate for both tests (ROC-AUC < 0.8), with the NISS performing significantly better than the ISS.

The NISS does not perform better than the ISS in penetrating injuries. However, this study was done on a low-risk trauma population, thus the results should not be extrapolated to high severity trauma. Due to statistical shortcomings in studies previously published, studies on far larger cohorts are necessary before the NISS should be adopted as the new "gold standard" for severity scoring.