Admission Red Blood Cell Distribution Width and Mean Platelet Volume as Predictors of Mortality in the Pediatric Intensive Care Unit: A Five-Year Single-Center Retrospective Study

<b>Background/Objectives:</b> Red blood cell distribution width (RDW) and mean platelet volume (MPV) are well-established prognostic biomarkers across various medical conditions. However, their role in predicting mortality among critically ill pediatric patients remains unclear. This study investigates the association between RDW, MPV, and 28-day mortality in pediatric intensive care unit (PICU) patients. <b>Methods</b>: This retrospective cohort study analyzed data from children aged 1 month to 18 years who were admitted to the PICUs at Chiang Mai University Hospital for ≥24 h between January 2018 and December 2022. The primary outcome was 28-day PICU mortality. A log-binomial regression analysis was conducted to assess the association of RDW and MPV with 28-day PICU mortality, adjusting for age, sex, mechanical ventilation, vasoactive drug use, continuous renal replacement therapy, and multiorgan failure. <b>Results</b>: A total of 580 PICU patients were included, 55.3% male, with a median age of 5.9 (IQR: 4.7-10.4) months. The 28-day PICU mortality rate was 9.8% (57/580). Respiratory failure and acute respiratory distress syndrome were the most common admission diagnoses (72.1%). Elevated RDW (≥15%) and MPV (≥10 fL) were independently associated with increased 28-day PICU mortality (adjusted RR: 2.73, 95% CI: 1.45-5.13 and 2.38, and 95% CI: 1.43-3.93, respectively). Both markers demonstrated high negative predictive values (RDW: 96.0% and MPV: 94.6%). <b>Conclusions</b>: Elevated RDW (≥15%) and MPV (≥10 fL) were independently associated with increased 28-day PICU mortality. These findings highlight their potential utility as accessible and cost-effective biomarkers for early risk stratification in critically ill pediatric patients.