A. Tatakis1, D. Wilson1, A. Farah1, C. Caswell1, W. Butak1, J. Gellings1, D. Holena1 1Medical College Of Wisconsin, Milwaukee, WI, USA
Introduction:
The accurate assessment of injury severity is crucial in trauma care as it helps stratify patients in research, serves as benchmarks for clinical care, and predicts outcomes. The Injury Severity Score (ISS) is one of the most common tools, which is measured by using the three most severely injured body regions. However, it underestimates injury severity when a patient has multiple injuries in one body region, as is often seen in penetrating trauma. The New Injury Severity Score (NISS) addresses this by using the three most severe injuries, irrespective of body region. We hypothesized that NISS would have better predictive accuracy than ISS for mortality in patients with penetrating thoracoabdominal injuries.
Methods:
A retrospective observational study of patients with penetrating thoracoabdominal injuries in Milwaukee County from 2018-2022 was conducted. The ISS and NISS were obtained for each patient and compared using Pearson’s pairwise correlation. Candidate variables were then examined including patient demographics, physiology, injury mechanism, ISS, and NISS in univariate logistic regression models for the outcome of inpatient mortality. Variables associated with mortality were defined as p≤0.2 and included in multivariable models. Two multivariable models were compared, one including ISS and the other including NISS using receiver operator characteristic curves. Statistical analysis was conducted using Stata v17.
Results:
There were 1,232 patients who met inclusion criteria over the study period. The median age was 30 (IQR 23-39) and the patients were 84.7% male. Gunshot wounds (GSW) accounted for 73.9% of injuries. The median initial systolic blood pressure (SBP) in the Emergency Department (ED) was 130 mmHg (IQR 113-144), and median ED Glasgow Coma Scale (GCS) was 15 (IQR 14-15). NISS and ISS were highly correlated (correlation 0.9, p<0.001), but overall NISS scores were higher than ISS scores (22 IQR [10-34] vs. 13 IQR [9-22], p< 0.001). In univariate analysis, initial ED SBP, initial GCS, age, GSW mechanism, NISS, and ISS were associated with mortality (p<0.2). In multivariable models including NISS or ISS, ROC curves were not significantly different (0.96 vs. 0.95, p=0.13, figure).
Conclusion:
While ISS and NISS scores correlated, the NISS scores were significantly higher, demonstrating the discrepancy in severity estimation between the two scoring systems. Despite this, there was no significant difference between ISS and NISS in predicting mortality outcomes in our study population. In patients with penetrating thoracoabdominal trauma, both the NISS and the ISS are acceptable measures of injury severity in mortality models.