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

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.

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).

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.

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.