IL-6 achieved good diagnostic performance for distinguishing TBI (AUC 0.974), metabolic/toxic encephalopathy (AUC 0.940), and hemorrhagic stroke (AUC 0.925) from healthy status; notably, IL-6 showed limited discriminatory power for differential diagnosis between TBI and other neurological diseases (AUC = 0.741). The gene discussed is IL6; the disease is nervous system disorder.