Prognostic value of procalcitonin and IL-6 with a composite model in moderate-severe traumatic brain injury

Inflammation is a critical secondary injury mechanism in craniocerebral trauma, which contributes to further tissue damage and long-term neurological deficits. This inflammatory response is primarily a neurotoxic injury mediated through the production of inflammatory factors by the inflammatory cells. Among these, IL-6 is the most promising biomarker for the clinical diagnosis of brain injury, and procalcitonin (PCT) is a promising biomarker specific for bacterial infection. This study aimed to investigate the relationship between IL and 6 and PCT concentrations at admission and the Glasgow Outcome Score (GOS) at 6 months post-discharge in patients with moderate-to-severe traumatic brain injury (TBI).

This retrospective study included 122 patients with moderate-to-severe TBI (Glasgow Coma Scale [GCS] 3-12) admitted to Shenzhen Second People's Hospital between January 2019 and June 2024. GOS scores at 6 months after discharge were recorded. Outcomes were dichotomized into favorable and unfavorable. Associations between IL and 6, PCT, and clinical characteristics were assessed via chi-square tests. Multivariate logistic regression identified independent prognostic factors for GOS, whereas ROC analysis evaluated the predictive performance (AUC) of biomarkers and composite models.

In total, 50 and 72 patients were categorized into the poor and good prognosis groups, respectively. Among these, 14 cases resulted in fatality. Initial serum analysis demonstrated significantly higher PCT (p < 0.001) and IL-6 (p = 0.001), but lower hemoglobin (p = 0.003) in the poor-prognosis group. Multivariate analysis identified six independent predictors of 6-month GOS outcomes: hemoglobin (OR = 1.03, p = 0.002), albumin (OR = 1.06, p = 0.035), IL-6 (OR = 1.00, p = 0.003), PCT (OR = 0.74, p = 0.015), GCS (OR = 1.49, p < 0.001), and creatinine (OR = 0.97, p = 0.001). Prognostic performance analysis demonstrated that the individual biomarkers IL-6 and PCT achieved AUC of 0.716 and 0.709, respectively. Notably, the composite model incorporating all six predictors exhibited a superior discriminative ability (AUC = 0.917).

PCT and IL-6 levels are associated with the outcomes of patients with moderate-to-severe TBI and may serve as effective prognostic indicators.