Prognosis prediction by urinary L-FABP in ICU patients admitted from the emergency department: a single-center, historical cohort study

Background Early risk stratification of critically ill patients is essential for optimizing intensive care unit (ICU) resource allocation and treatment decisions. Urinary liver-type fatty acid-binding protein (L-FABP) is a simple, noninvasive biomarker that may provide real-time information on organ dysfunction. However, its prognostic utility in patients admitted to the ICU from the emergency department remains unclear. Methods This single-center retrospective observational study included patients admitted to the ICU between December 2020 and August 2022. Urinary L-FABP concentrations were measured at ICU admission (T0) and 3 hours later (T3). The primary outcome was 28-day in-hospital mortality. Prognostic performance was assessed using receiver operating characteristic (ROC) curves and Cox proportional hazards models with inverse probability of treatment weighting (IPTW). Results were compared with APACHE II, SOFA scores, and lactate levels. Results A total of 118 patients (median age: 69 years [interquartile range (IQR) 51–82]; 72 males [61.0%]) were included in the final analysis. Urinary L-FABP at T3 showed the highest predictive performance for 28-day mortality (area under the curve [AUC] = 0.873), outperforming APACHE II (AUC = 0.801), SOFA (AUC = 0.753), and lactate (AUC = 0.734). Elevated L-FABP (T3) was independently associated with increased mortality (hazard ratio [HR] = 8.60, 95% confidence interval [CI]: 1.02–72.64, P = 0.047). The T3/T0 ratio showed only modest predictive value (AUC = 0.623). Conclusions Urinary L-FABP levels measured 3 hours after ICU admission were a strong and independent predictor of short-term mortality. Its simplicity and bedside applicability suggest its potential utility not only in ICUs but also in emergency departments and triage decision-making.