Interleukin-6 and its association with outcome in traumatic brain injury: a prospective cohort

BACKGROUND: Traumatic brain injury (TBI) continues to be a major cause of death and disability worldwide. Biomarkers for treatment and prognostication are needed for counseling and clinical management. OBJECTIVE: In this study, we evaluated the ability of serum IL-6 to predict mortality and disability in a population whith moderate and severe TBI (msTBI). METHODS: Adult patients with msTBI were included consecutively from December 2019 to August 2023. Clinical data were collected during hospital stays and functional outcome was established at 6 months using GOSE. Serum IL-6 levels were measured on day 0, day 3 and day 7 after injury. RESULTS: Eighty-eight patients were recruited and completed 6-month follow-up. Clinical variables associated with the 6-month adverse outcome were admission GCS (OR 0.77 95% CI 0.67-0.87, p < 0.001), age (OR 1.10 95% CI 1.03-1.1, p = 0.001), Rotterdam score (OR 2.8 95% CI 1.7-5.0, p < 0.001), hospital infections (OR 4.7 95% CI 1.9-12.1, p < 0.001) and day-0 IL-6 (OR 1.1 95% CI 1.08-1.13, p < 0.001). When adjusted for age, severity of injury,and the presence of a hospital infection, day-0 IL-6 was significantly associated with the adverse outcome at 6 months (OR 1.15 95% CI 1.1-1.2, p = 0.031). Area under the curve (AUC) of 89% (95% CI 82%-96%). Calculated sensitivity and specificity were 75% and 89%, respectively, at a cut-off point of 59 pg/ml. CONCLUSION: In a population of msTBI, levels of serum interleukin-6 within the first 24 h after injury is an independent predictor of 6-month mortality and disability with a net benefit in clinical decision-making across relevant threshold probabilities.