Platelet-to-White Blood Cell Ratio as a Predictor of ICU Mortality in Septic Shock and Heart Failure: A Real-World Validation Study Using the MIMIC-eICU and a Chinese Cohort

Background: The platelet-to-white blood cell ratio (PWR) has been associated with adverse outcomes in critically ill patients. Nonetheless, its prognostic significance in individuals with concurrent septic shock and heart failure remains insufficiently validated externally. This study sought to examine this association utilizing a large public database and to validate the findings in an independent real-world cohort. Methods: This retrospective cohort study included adult patients with septic shock and heart failure. The discovery cohort was derived from the MIMIC-IV and eICU databases. The validation cohort was retrospectively collected from The Central hospital of Enshi Tujia and Miao Autonomous Prefecture (August 2023–June 2025). The primary outcome was ICU mortality. Multivariable Cox regression, Kaplan-Meier analysis, and subgroup analyses were performed. Results: The study incorporated 934 patients in the discovery cohort and 124 patients in the validation cohort. In the discovery cohort, restricted cubic spline analysis demonstrated a linear relationship between platelet-to-white blood cell ratio (PWR) and mortality (nonlinearity P =0.655), prompting a tertile-based classification (Q1: ≤ 9.95; Q2: > 9.95–≤ 17.72; Q3: > 17.72). Compared to Q1, Q3 was associated with significantly reduced ICU mortality in the fully adjusted model (HR 0.66, 95% CI 0.44– 0.99). Applying the same cut-off (9.95) in the validation cohort, patients with a low PWR (≤ 9.95) exhibited significantly higher mortality compared to those with a high PWR (> 9.95) (HR 3.11, 95% CI 1.46– 6.66; log-rank P =0.002). Subgroup analyses substantiated the robustness of these findings. Conclusion: A reduced platelet-to-white blood cell ratio serves as an independent predictor of elevated ICU mortality among patients experiencing septic shock and heart failure. This straightforward and cost-effective biomarker demonstrated a consistent association in an external real-world cohort, underscoring its potential utility for early risk stratification.