Prognostic value of neuropeptide proenkephalin A in patients with severe traumatic brain injury

•Plasma proenkephalin A levels increased in patients with traumatic brain injury.•Proenkephalin A could possibly serve as a novel biomarker in traumatic brain injury.•Proenkephalin A may be a good prognostic factor for clinical outcome of traumatic brain injury. High plasma proenkephalin A levels have been associated with poor clinical outcome of aneurysmal subarachnoid hemorrhage. This prospective observatory study was designed to investigate the relationship between plasma proenkephalin A levels and 1-week mortality, 6-month mortality and 6-month unfavorable outcome (defined as Glasgow Outcome Scale score of 1–3) in patients with severe traumatic brain injury. This study recruited 128 patients and 128 sex- and age-matched healthy controls. Plasma proenkephalin A levels, as measured by chemoluminescence sandwich immunoassay, were statistically significantly higher in patients than in healthy controls (239.1±93.0pmol/L vs.81.3±22.1pmol/L; P