Novel Fibrinogen- and Procalcitonin-Based Composite Ratios for Mortality Prediction in Pediatric Trauma

Background: Composite biomarkers combining inflammatory or metabolic markers with a negative acute-phase protein predict outcomes in critically ill patients, but fibrinogen-based ratios grounded in the “lethal triad” of trauma-induced coagulopathy remain unexplored in pediatric trauma. We evaluated novel lactate/fibrinogen (LFR) and procalcitonin/fibrinogen (PFR) ratios alongside the procalcitonin/albumin ratio (PAR), a composite triple inflammation–perfusion index (TIPI, combining procalcitonin, CRP, and lactate relative to albumin), and established albumin-based ratios and severity scores for mortality prediction. Methods: In this retrospective cohort study, 200 pediatric trauma patients admitted to the PICU of İzmir City Hospital (27 October 2023–27 October 2025) were analyzed. All ratios were calculated serially over the first 72 h and at PICU discharge. Discrimination was assessed by ROC analysis. Independent predictors were identified using Firth penalized logistic regression, with bootstrap validation (B = 1000). Results: Thirteen patients (6.5%) died. LFR achieved the highest point-estimate discrimination (AUC 0.848), numerically exceeding LAR (0.829), though not significantly (p = 0.399). PAR, TIPI, and PFR were also independently associated with mortality (all p < 0.05), whereas CAR and NLR were not. LFR correlated strongly with LAR (ρ = 0.873), indicating overlapping information despite differing denominators. Serial trajectories provided only limited, largely inconclusive incremental value. A sensitivity analysis including early deaths and rapid discharges (n = 274) confirmed LFR/LAR’s robust discrimination. but not that of PAR, TIPI, or PFR. Conclusions: Lactate-based ratios showed the strongest single-timepoint discrimination, with the novel LFR performing comparably to LAR via a distinct coagulopathy-based mechanism. Lactate- and fibrinogen-based ratios were robust to inclusion of early deaths, whereas inflammation-based ratios were not, indicating that biomarker validity may depend on injury-to-death timing in pediatric trauma.