Diagnostic and prognostic significance of suPAR in traumatic brain injury

Soluble urokinase plasminogen activator receptor (suPAR) is a highly sensitive marker that reflects increased inflammation and is positively correlated with pro-inflammatory biomarkers. The aim of this prospective observational study was to explore the relationship between the plasma concentration of suPAR and traumatic brain injury (TBI).

In all 112 patients with TBI were included. Patients coming within 12 h whose highest abbreviated injury score (AIS) was 3 or less (other than head injury) were considered to be isolated TBI. Blood samples were obtained on admission. In all ninety healthy volunteers were enrolled as control group. Levels of plasma suPAR were determined using an enzyme-linked immunosorbent assay (ELISA) kit according to the manufacturer's instructions. Plasma D-dimer was measured and Glasgow Coma Scale (GCS) score was assessed at the same time.

Plasma suPAR values were statistically significantly higher in TBI patients than in controls (patients; 14.89 ± 6.94, controls; 2.79 ± 0.69, P < 0.01). The suPAR levels were strongly associated with the severity of TBI patients. The suPAR levels increased in association with the severity of brain injury, significance being found among all three groups: severe, moderate and mild TBI. The suPAR levels in non-survivals were significantly increased compared to the survivals (P < 0.05). Plasma levels of suPAR were strongly correlated to the GCS score (r = -0.854) and the levels of D-dimer (r = 0.753, both P < 0.01). Receiver operating characteristic curve (ROC) analysis of suPAR levels indicated that suPAR values had a high diagnostic specificity and sensitivity to differentiate survivals from non-survivals, the area underneath the ROC curve (AUROC) was 0.801 (95% CI: 0.698-0.903). The optimal suPAR cut-off value in predicting mortality was 15.70 ng/ml (sensitivity: 70.4%; specificity: 65.9%).

Plasma levels of suPAR are elevated in TBI patients. Prognosis was worse in the patient group with elevated suPAR. High suPAR levels indicate a poorer prognosis in TBI patients.