The Neutrophil-to-lymphocyte Ratio at the Time of Admission: A New Prognostic Indicator for Hospital Mortality of Trauma Patients

Abstract

The elevated neutrophil-to-lymphocyte ratio (NLR) is associated with poor clinical outcomes, especially in pro-inflammatory states such as surgical injuries and severe hemorrhages. Therefore, it was hypothesized whether NLR value at the time of admission could be a prognostic indicator of hospital mortality in trauma patients. This retrospective cohort study was conducted on 865 trauma patients referred to Rajaee Hospital between April 2016 and July 2019. The NLR value was calculated at the time of admission, and receiver operating characteristics (ROC) curve analysis was used to determine the cut-off point value of admission NLR related to hospital mortality of trauma patients. Furthermore, Kaplan-Meier survival analysis and Cox regression models have been applied to determine the effectiveness and prognostic potential of the admission NLR in the hospital mortality of trauma patients. The median age of the trauma patients was 32 years with an interquartile range (IQR) of 23 to 48 years, and most of them were male (83.9%). Also, trauma patients had a median injury severity score (ISS) of 9 (IQR=4-16) and a median Glasgow coma scale (GCS) of 14 (IQR=9-15). The cut-off value for admission NLR was 5.27 (area under the curve: 0.642, 95%CI: 0.559-0.726, p=0.001). In Kaplan-Meier survival analysis, the admission NLR>5.27 was an indicator of hospital mortality in trauma patients (p=0.001). Multivariate Cox regression models demonstrated that trauma patients with an admission NLR>5.27 had a 2.33-fold risk of hospital mortality (hazard ratio=2.33, 95%CI: 1.02-5.38, p=0.041). Furthermore, the admission NLR>5.27 was associated with a higher risk of hospital mortality in trauma patients with age≥65 years, systolic blood pressure≤90 mmHg, blood potassium>4.5 mmol/L, blood sodium>144 mEq/L, blood potential hydrogen (pH)≤7.28, GCS≤8, ISS>24 and blood base excess≤-6.1 mEq/L. The NLR value greater than 5.27 at the time of admission was associated with poorer outcomes, and it can be considered an independent prognostic indicator of hospital mortality in trauma patients.