C-reactive protein-to-albumin ratio as a predictor of 28-day mortality in critically ill pediatric patients: a retrospective cohort study

This large-scale real-world study aimed to evaluate whether the C-reactive protein-to-albumin ratio (CAR), an indicator of systemic inflammation and nutritional status, predicts 28-day mortality in critically ill pediatric patients. Retrospective cohort study. We analyzed data from 8,000 children admitted to a tertiary pediatric intensive care unit (PICU) in China between 2010 and 2019. CAR was calculated using initial CRP and albumin levels upon admission. Patients were stratified into quartiles based on CAR values. The primary outcome was 28-day all-cause mortality; in-hospital mortality was a secondary outcome. Multivariable Cox regression and Kaplan–Meier survival analyses were performed, along with subgroup analyses to validate robustness. Higher CAR levels were significantly associated with increased 28-day mortality. Patients in the highest CAR quartile had a hazard ratio of 1.51 (95% CI: 1.07–2.13; p = 0.018) compared with the lowest quartile. The fully adjusted model including CAR achieved an AUC of 0.820 (95% CI: 0.798–0.843), indicating good discriminatory ability. Kaplan-Meier curves confirmed reduced survival in the high CAR group (p = 0.0042). The association remained consistent across all subgroups. CAR is significantly associated with short-term mortality in critically ill children. As a low-cost, easily accessible biomarker, CAR may serve as a valuable early risk stratification tool in real-world pediatric intensive care settings.