Association of Neutrophil-to-Prognostic Nutritional Index Ratio With Prognosis in Critically Ill Patients Undergoing Gastric Procedures

Introduction Inflammation and malnutrition frequently coexist in critically ill patients, yet single inflammatory or nutritional indices capture only part of this state. We examined how the preoperative neutrophil-to-prognostic nutritional index ratio (NPNI), a composite of both, relates to mortality across follow-up in patients undergoing gastric procedures. Methods We studied 1821 adults in the Medical Information Mart for Intensive Care-IV database who underwent a gastric procedure. The primary outcome was in-hospital mortality; secondary outcomes included 15-d, 30-d, 60-d, 90-d, 1-y, 3-y, and 5-y mortality. Logistic regression, time-window Cox models, and landmark analysis were used to assess the association between NPNI and mortality. Receiver operating characteristic curves were generated to calculate the area under the curve. The signal source of NPNI was explored through interaction analysis between the inflammatory axis (neutrophils) and the nutritional axis (Onodera Prognostic Nutritional Index). Results Higher NPNI was associated with greater odds of death at every horizon (per 1 standard deviation, odds ratio (OR) in -hospital = 1.24, 95% confidence interval: 1.10-1.40; OR 5-y = 1.28, 95% confidence interval: 1.15-1.42). NPNI demonstrated "cross-temporal stability," maintaining significant associations in both the early mortality (0-30 d) and late mortality (30 d-5 y) windows. Time-window analysis revealed that the nutritional axis was associated with early mortality (heart rate=0.81, P = 0.032), while the inflammatory axis was associated with late mortality (heart rate=1.13, P < 0.001). The interaction between the two axes was subadditive (relative excess risk due to interaction=−0.32). NPNI showed modest discriminative ability (area under the curve: 0.568), inferior to Simplified Acute Physiology Score II (0.647) and Oxford Acute Severity of Illness Score (0.625). Conclusions Elevated NPNI is an independent risk factor for mortality in critically ill patients undergoing gastric procedures. Its value lies in cross-temporal risk integration rather than discriminative ability.