Admission Neutrophil-to-Platelet Ratio as an Independent Predictor of Mortality in Critically Ill Patients with AECOPD: A MIMIC-IV Database Analysis

Background Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are critical events with high mortality. The neutrophil-to-platelet ratio (NPR) has emerged as a promising systemic inflammatory marker, but its prognostic value in AECOPD remains underexplored. Methods This retrospective cohort study utilized data from the MIMIC-IV 3.1 database (2008–2022). Patients with AECOPD were categorized into quartiles based on admission NPR. The primary outcome was in-hospital mortality; the secondary outcome was 28-day mortality. Multivariable Cox regression, restricted cubic splines (RCS), and subgroup analyses with False Discovery Rate (FDR) adjustment were performed. Results Among 1,137 patients, in-hospital and 28-day mortality rates were 15.5% and 14.1%, respectively. In the fully adjusted model (Model IV), the highest NPR quartile (Q4, > 0.06) was associated with a 3.01-fold increased risk of in-hospital mortality (HR 3.01, 95% CI 1.31–6.89, P = 0.009) and nearly triple the risk of 28-day mortality (HR 2.91, 95% CI 1.18–7.16, P = 0.020) compared to Q1. RCS confirmed a linear risk trajectory (P_ non-linearity = 0.796). Significant interactions were observed for sepsis status (P_FDR < 0.001), with NPR showing higher sensitivity in non-septic patients (HR 4.66, 95% CI 1.24–17.56). Adding NPR significantly improved model discrimination (C-index: 0.7098 to 0.7182, P = 0.036) and clinical net benefit in decision curve analysis. Conclusions Admission NPR is a potent, independent predictor of mortality in AECOPD, particularly in younger and clinically less complex populations. Incorporating NPR into risk stratification may enhance early clinical decision-making.