Utility of Serum Growth Arrest-Specific Protein 6 as a Biomarker of Severity and Prognosis After Severe Traumatic Brain Injury: A Prospective Observational Study

OBJECTIVE: Growth arrest-specific protein 6 (Gas6) may harbor protective effects in acute brain injury. This study was designed to determine the relation of serum Gas6 levels to severity and prognosis after traumatic brain injury (TBI). METHODS: In this prospective cohort study of 114 controls and 114 patients with severe TBI, multivariate analysis was used to assess relationships between serum Gas6 levels, Glasgow coma scale (GCS) score, Rotterdam computed tomography (CT) score, postinjury 180-day mortality, overall survival and poor prognosis (Extended Glasgow outcome scale score 1–4). RESULTS: Significantly increased serum Gas6 levels of patients (median, 10.3 ng/mL versus 32.5 ng/mL; P < 0.001), as compared with controls, were independently correlated with Rotterdam CT score (t = 3.629, P < 0.001) and GCS score (t=−3.393, P = 0.001), and independently predicted 180-day mortality (odds ratio, 1.078; 95% confidence interval (CI), 1.007–1.154), overall survival (hazard ratio, 1.074; 95% CI, 1.012–1.139) and poor prognosis (odds ratio, 1.129; 95% CI, 1.059–1.205). Areas under receiver operating characteristic curve (AUCs) of serum Gas6 levels for discriminating risks of 180-day mortality and poor prognosis were 0.785 (95% CI, 0.699–0.857) and 0.793 (95% CI, 0.707–0.863), respectively; and serum Gas6 levels above 30.9 ng/mL and 28.3 ng/mL predicted 180-day mortality and poor prognosis with maximum Youden indices of 0.451 and 0.468, respectively. The predictive ability of serum Gas6 levels for mortality was similar to those of GCS score (AUC, 0.833; 95% CI, 0.751–0.896; P = 0.286) and Rotterdam CT score (AUC, 0.823; 95% CI, 0.740–0.888; P = 0.432). The discriminatory capability of serum Gas6 levels for the risk of poor prognosis was in the range of GCS score (AUC, 0.846; 95% CI, 0.766–0.906; P = 0.178) and Rotterdam CT score (AUC, 0.831; 95% CI, 0.750–0.895; P = 0.368). CONCLUSION: Serum Gas6 may appear as a promising biochemical parameter for aiding in the assessment of trauma severity and prediction of prognosis among patients with severe TBI.