Neutrophil percentage-to-albumin ratio and in-hospital mortality after emergency repair of ruptured abdominal aortic aneurysm: a retrospective cohort study

Abstract Background Rupture is the most catastrophic presentation of abdominal aortic aneurysm (AAA). Despite emergency repair, ruptured abdominal aortic aneurysm (RAAA) remains associated with high mortality, and prognosis is difficult to predict. This study examined whether admission neutrophil percentage-to-albumin ratio (NPAR) was associated with in-hospital mortality in patients with RAAA. Methods We retrospectively analyzed patients who underwent RAAA surgery between January 2004 and December 2025. Patients were classified as survivors or non-survivors according to in-hospital outcome. Receiver operating characteristic (ROC) analysis, logistic regression, and restricted cubic spline modeling were used to assess the association between NPAR and in-hospital mortality. Firth penalized logistic regression sensitivity analyses and temporal sensitivity analyses were also performed. Results Among 121 patients, 91 survived and 30 died during hospitalization. NPAR showed moderate-to-good discriminatory performance for in-hospital mortality, with an area under the curve (AUC) of 0.811 (95% confidence interval [CI], 0.726–0.896). The ROC-derived cutoff value was 2.595, with a sensitivity of 90.0% and a specificity of 71.4%. NPAR had a higher AUC than the neutrophil-to-lymphocyte ratio (AUC, 0.693) and the modified Harborview Risk Score (AUC, 0.700). Higher NPAR was associated with increased odds of in-hospital mortality in conventional logistic regression models, and Firth penalized logistic regression yielded consistent adjusted estimates (OR range, 4.273–6.858; all P < 0.001). The association remained significant after adjustment separately for treatment era and calendar year. Restricted cubic spline analysis suggested a potentially steeper increase in mortality risk at higher NPAR levels, although evidence for nonlinearity did not reach statistical significance (P for nonlinearity = 0.076). Conclusions Admission NPAR was associated with in-hospital mortality after emergency RAAA repair and may warrant further evaluation as a simple adjunct for early risk stratification. External validation is required before clinical implementation.