Admission FDP and D-Dimer Predict Functional Outcomes in Closed TBI: A Single-Center Retrospective Cohort Study

<jats:p>Coagulopathy is a frequent complication after traumatic brain injury (TBI), yet few studies directly compare fibrin degradation products (FDP) and D-dimer as independent predictors of discharge functional impairment evaluated by modified Rankin Scale (mRS) in mild-to-moderate closed TBI. This single-center retrospective cohort enrolled 140 consecutive closed TBI inpatients to compare the independent prognostic value of admission FDP and D-dimer for discharge mRS. Ordinal logistic regression with three adjustment schemes and restricted cubic spline (RCS) modeling was adopted to assess predictive effects and nonlinear relationships, while negative binomial regression analyzed their correlation with hospital length of stay (LOS). After full confounder adjustment, admission FDP independently predicted poor functional outcome (OR = 1.749, 95% CI 1.019–3.002, P = 0.042) with an evident nonlinear threshold effect, whereas D-dimer lost statistical significance (P = 0.075); neither marker was associated with LOS (all P &amp;gt; 0.05). These findings indicate that admission FDP is a superior, specific independent biomarker for predicting discharge functional disability in closed TBI compared with D-dimer, and can support early clinical risk stratification.</jats:p>