Blood biomarker outliers and clinical events during intensive care in patients with traumatic brain injury.

Introduction: Monitoring and timely clinical assessment are fundamental to treating patients with traumatic brain injury (TBI) in the intensive care unit (ICU). Proactive, individualised treatment is unavailable with the current methods. Research question: How do outlying blood biomarker levels associate with clinical events or outcome in TBI? Materials and methods: Glial fibrillary acidic protein (GFAP), neurofilament light (NfL), interleukin-10 (IL-10) and total tau (t-tau) were analysed from blood plasma samples of 70 ICU-treated patients, aged ≥18, with a clinical diagnosis of TBI and an indication for a head CT scan. The blood samples were collected on arrival and on days 1, 2, 3 and 7. The biomarkers were screened for outliers and biomarker values outside Q1-1.5 × interquartile range (IQR) or Q3+1.5 × IQR on any day post-injury were considered outliers. The outlier group was compared with the non-outlier group targeting clinically significant aspects such as high intracranial pressure, seizures/status epilepticus, or mortality/poor outcome. The Glasgow Outcome Scale Extended (GOSE) was evaluated between 6 and 12 months after the injury. Results: Difference was found in epileptic activity (n = 7 vs n = 0) and the number of performed decompressive hemicraniectomies (n = 6 vs n = 0) between the outlier and the non-outlier groups, p = 0.015 and < 0.0001, respectively. Patients in the outlier group were also more likely to have a poor outcome (GOSE 1-3) than patients in the non-outlier group, p = 0.011. Discussion and conclusion: Biomarker outliers seem to associate with clinical events and poor outcome in ICU-treated patients with TBI, possibly due to greater severity of TBI.