Association between early albumin-corrected neutrophil-to-lymphocyte ratio and in-hospital mortality in critically ill patients with pneumonia: a retrospective cohort study based on MIMIC-IV and eICU-CRD

Abstract Background The association between early albumin-corrected neutrophil-to-lymphocyte ratio (ACNLR) and in-hospital mortality in critically ill patients with pneumonia remains unclear. This study aimed to clarify this relationship using two large critical care databases. Methods Patients with pneumonia were retrospectively identified from the Medical Information Mart for Intensive Care IV (MIMIC-IV) and the eICU Collaborative Research Database (eICU-CRD). ACNLR was calculated as the neutrophil-to-lymphocyte ratio divided by serum albumin concentration using laboratory measurements obtained within the first 24 hours after intensive care unit admission. Multivariable logistic regression and restricted cubic spline analyses were used to investigate the association between ACNLR and in-hospital mortality. Subgroup analyses and propensity score-based sensitivity analyses were also performed. Results A total of 1,378 patients from MIMIC-IV and 3,426 patients from eICU-CRD were included. In-hospital mortality was 27.4% and 16.8%, respectively. Higher ACNLR was independently associated with increased in-hospital mortality after multivariable adjusting. In the fully adjusted model, each 1-standard deviation increase in ACNLR was associated with higher mortality in both MIMIC-IV (OR = 1.19, 95% CI: 1.06–1.33, P = 0.003) and eICU-CRD (OR = 1.28, 95% CI: 1.16–1.41, P < 0.001). Patients in the highest ACNLR quartile also had significantly higher mortality than those in the lowest quartile in both cohorts. Restricted cubic spline analyses showed a nonlinear positive association between ACNLR and in-hospital mortality, with consistent findings across sensitivity analyses. Conclusions Higher early ACNLR was independently associated with increased in-hospital mortality in critically ill patients with pneumonia. ACNLR may serve as a simple and readily biomarker for early mortality risk stratification in pneumonia-related critical illness.