Association between platelet-to-white blood cell ratio and short-term prognosis in patients with acute myocardial infarction: a retrospective cohort study

Background Clinical evidence regarding the prognostic value of the platelet-to-white blood cell ratio (PWR) for short-term outcomes in patients with acute myocardial infarction (AMI) remains limited, particularly its independent predictive role for in-hospital and ICU all-cause mortality, which lacks validation in large-scale, multi-center settings. This study investigated the association between PWR and in-hospital and ICU mortality in AMI patients, aiming to evaluate its impact on short-term prognosis in this population. Methods This retrospective cohort study included 2,381 AMI patients from the MIMIC-IV database as the derivation cohort, with validation performed in 7,054 AMI patients from the multi-center eICU-CRD database and 252 AMI patients from a single-center internal cohort. Restricted cubic spline and Kaplan–Meier analyses were used to assess nonlinearity and survival differences. Multivariable logistic regression examined the independent association between PWR and in-hospital and ICU mortality. Decision curve analysis assessed the clinical utility of PWR. Subgroup analyses, Cox regression, Fine-Gray competing-risk models, and mediation analyses were conducted for robustness assessment and mechanistic exploration. Results In the derivation cohort of this study, 316 patients (13.3%) died during hospitalization and 237 (10.0%) died during ICU stay. Restricted cubic spline analysis demonstrated a consistent linear relationship between PWR and the risks of in-hospital and ICU mortality. Multivariable logistic regression revealed a significant inverse association between PWR and in-hospital mortality (OR = 0.976, 95% CI: 0.960–0.991, P = 0.003) as well as ICU mortality (OR = 0.977, 95% CI: 0.959–0.994, P = 0.012). The robustness of this inverse association was further supported by Cox regression and Fine-Gray competing-risk models. The results were consistently reproduced in both the external eICU-CRD validation cohort and the single-center internal validation cohort. Additionally, Kaplan–Meier curves showed that patients in the higher PWR group had significantly better cumulative survival than those in the lower PWR group. Decision curve analysis further showed that PWR provided some net benefit at clinically relevant thresholds for both outcomes, supporting its clinical utility. In subgroup analyses, the inverse association between PWR and short-term mortality remained directionally consistent across all subgroups, with no significant interactions after Benjamini–Hochberg FDR correction. Mediation analysis indicated that SAPS II score and vasopressor use mediated 25.9% and 18.6% of the protective effect of PWR, respectively. Conclusions PWR is a simple, low-cost composite marker derived from routine complete blood counts. It is significantly and inversely associated with short-term in-hospital and ICU mortality in AMI patients. Our findings suggest that PWR may serve as a convenient and inexpensive adjunctive tool for early risk stratification and identification of high-risk individuals. However, its clinical application warrants further validation in larger, multi-center prospective studies.