Hematological-nutritional indices in the pediatric intensive care unit: clinical significance of the lymphocyte-based prognostic nutritional index in critically ill children and adolescents – a prospective cohort study

Background The lymphocyte-based prognostic nutritional index (PNI) is a well-established prognostic tool. Still, its utility in the pediatric intensive care unit remains uncertain, particularly in resource-limited settings where simple, cost-effective markers are essential. This study aimed to evaluate the association between PNI and clinical outcomes, including mortality, in critically ill children and adolescents. Patients and methods A prospective cohort study was conducted on 291 patients (aged 4 months to 15.5 years) admitted to a tertiary care pediatric intensive care unit. PNI was calculated at admission using the formula: lymphocyte count (cells/μl)×0.005+serum albumin (g/dl)×10. Patients were stratified into low-PNI and high-PNI groups using an optimal cutoff of less than or equal to 49, determined by receiver operating characteristic analysis to predict 90-day mortality. Results Nonsurvivors represented 30.9% ( n =90). Mortality was significantly higher in the low-PNI group than in the high-PNI group (46.3 vs. 11.6%, P <0.001). Low PNI was associated with higher rates of mechanical ventilation (53.7 vs. 27.9%, P <0.001), sepsis (57.4 vs. 39.5%, P =0.002), and higher severity scores (Pediatric Risk of Mortality and Sequential Organ Failure Assessment; P <0.001). At the less than or equal to 49 cutoff, PNI predicted 90-day mortality with an area under the curve of 0.704 ( P <0.001) and 83.3% sensitivity. Kaplan–Meier analysis showed reduced survival in the low-PNI group, with higher mortality risk at 30 days [hazard ratio (HR): 3.25, P <0.001] and 90 days (HR: 2.18, P =0.002). Multivariate analysis confirmed PNI less than or equal to 49 as an independent predictor of mortality (HR: 3.09, P <0.001). Conclusion PNI is a simple, reliable, and independent marker for predicting adverse outcomes in critically ill pediatric patients, with a broad applicability in resource-constrained settings.