Correlation Between Low Platelet-to-Lymphocyte Ratio and High Mortality Rates in Adult Trauma Patients With Moderate-to-Severe Brain Injuries.

Background: White blood cell (WBC) subtypes reflect immune and inflammatory conditions in patients. This study aimed to examine the association between the ratio of platelets to WBC subtypes and mortality outcomes in patients with moderate-to-severe traumatic brain injury (TBI). Method: The Trauma Registry System of the hospital was retrospectively reviewed to gather medical records of 2397 adult patients who were hospitalized from 2009 to 2020 and had moderate-to-severe TBI with a head abbreviated injury scale (AIS) score of 3 or higher. The monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) were compared between the survivors (n = 2, 138) and nonsurvivors (n = 259). A multivariate logistic regression analysis was performed to investigate the independent effects of the univariate prognostic factors on mortality outcomes. The survival variations among the PLR subgroups were evaluated by the Kaplan-Meier survival analysis including a log-rank test. Results: The PLR of the deceased patients was considerably lower than that of the survivors (129.5 ± 130.1 vs. 153.2 ± 102.1, p < 0.001). However, no significant differences were observed in monocyte and neutrophil counts, MLR, or NLR between the deceased and survivor groups. A lower PLR was recognized as an independent risk factor for mortality (odds ratio: 1.26, 95% confidence interval: 1.06-1.51, p=0.010). The receiver operating characteristic (ROC) established PLR as the most strong predictor among the three ratios (area under the ROC curve = 0.627, sensitivity = 0.846, and specificity = 0.382, according to the cut-off value = 68.57). When the patient groups were divided by PLR quartile, the Kaplan-Meier analysis showed significantly worse survival in the lowest PLR quartile group (< 83.1) compared with the highest quartile group (≥ 189.1) (p < 0.001). Conclusion: Lower PLR is associated with greater mortality in adult patients with moderate-to-severe TBI. PLR may be a valuable measure for classifying mortality risk in this population.