Prognostic value of neutrophil-lymphocyte ratio (NLR) in trauma patients.

Background: Trauma mortality exhibits three peaks: immediate, early, and late post-traumatic. Early deaths are often due to haemorrhage and central nervous system injury, whereas late deaths are associated with sepsis and multi-organ failure. The neutrophil-lymphocyte ratio (NLR) is a readily available and inexpensive marker of inflammation, and its prognostic value under various conditions has been established. However, the predictive ability of the NLR in trauma mortality remains unclear, with conflicting results from previous studies. This study aimed to investigate the correlation between NLR (on admission and at 48-hour post-admission) and trauma outcomes.

Methods: This retrospective study analysed data of trauma patients (≥ 18 years old) of which 372 were admitted to a level one trauma unit between January and June 2017. The data collected included demographics, mechanism of injury, injury severity score (ISS), new injury severity score (NISS), abbreviated injury scale (AIS), hospital length of stay (LOS), hospital disposition, and NLR values on admission and at 48 hours. Logistic regression models were used to analyse the association between the NLR and mortality, controlling for age, sex, ISS, and AIS. The sample size was calculated based on the anticipated mortality rate and desired power.

Results: The study included 288 patients for admission NLR analysis and 165 patients for the 48-hour NLR analysis. While factors such as ISS, NISS, emergency department (ED) probability of survival, NISS EU probability, and hospital disposition significantly predicted mortality, NLR at both 24 and 48 hours was not significantly associated with mortality. Although NLR showed good diagnostic accuracy, it did not improve the predictive power of the models, including established prognostic factors. The small sample size for 48-hour NLR analysis is a limitation.

Conclusion: Although the NLR is a simple indicator of systemic inflammation, this study found that it does not independently predict mortality in trauma patients when other established prognostic markers are included. These findings suggest that NLR has limited additional prognostic value in this context, highlighting the importance of incorporating established injury severity scores and other clinical factors for accurate mortality risk assessment. Further research with larger sample sizes is needed to confirm these findings and explore the potential role of the NLR in predicting other trauma outcomes.