Early antithrombin depletion after trauma is associated with biomarkers of endotheliopathy and systemic protein loss: a retrospective observational study.

BACKGROUND: Early antithrombin (AT) depletion after trauma may result from thrombin-related consumption, vascular leakage, and systemic protein loss. We examined the biomarker profile associated with early AT depletion and whether reduced AT activity identifies an adverse early injury phenotype. METHODS: In this single-center retrospective observational study, 100 adult trauma patients were analyzed on admission. AT activity, albumin (Alb), syndecan-1 (SDC-1), and thrombin-antithrombin complex (TAT) were measured in residual blood samples obtained at hospital arrival. Associations among biomarkers were assessed using locally estimated scatterplot smoothing and generalized additive models. LASSO and elastic-net regression identified variables associated with AT activity, and exploratory Bayesian regression assessed directional associations. Clinical outcomes were compared between patients with reduced (<80%) and preserved (≥80%) AT activity. RESULTS: Reduced AT activity was present in 32% of patients and remained associated with shock (adjusted OR 9.42, 95% CI 1.32-109.00, p=0.037) and disseminated intravascular coagulation (DIC) (adjusted OR 12.20, 95% CI 2.17-113.00, p=0.010) after adjustment for age, sex, ISS, and lactate. AT activity was positively associated with Alb and negatively associated with SDC-1 and TAT. In regularized regression, Alb and SDC-1 were more consistently associated with AT activity, whereas TAT was not selected. Bayesian analyses showed stronger directional evidence for Alb and SDC-1 than for TAT. CONCLUSION: Early AT depletion after trauma was associated with adverse clinical features and biomarker patterns consistent with endothelial injury and circulating protein depletion, beyond thrombin-related consumption alone.