Systemic Immune-Inflammation Index is Associated with Pressure Injury in Hospitalized Patients with Non-Small Cell Lung Cancer: A Retrospective Cohort Study

Abstract

Objective To examine the association between admission systemic immune-inflammation index (SII) and incident pressure injury (PI) in hospitalized patients with non-small cell lung cancer (NSCLC) and assess its discriminative performance. Materials and Methods This single-center retrospective cohort included 428 hospitalized patients with NSCLC (119 with PI and 309 without PI). Admission SII was calculated from platelet, neutrophil, and lymphocyte counts. Logistic regression and ROC analyses were performed, with DeLong comparisons, bootstrap internal validation, calibration, and decision-curve analysis. Results Patients with PI had higher SII than those without PI (median 1223.49 [IQR 963.35–1519.65] vs 868.37 [694.89–1089.19], P < 0.001). In multivariable analysis, SII (OR per 100 units = 1.339, 95% CI: 1.223–1.466), BMI (OR = 0.549, 95% CI: 0.467–0.645), and CRP (OR = 1.254, 95% CI: 1.173–1.341) were independently associated with PI. The AUC was 0.763 for SII and 0.908 for the combined SII-BMI-CRP model; bootstrap optimism-corrected AUC was 0.904 (95% CI: 0.878–0.934). Conclusion Higher admission SII was independently associated with incident PI and showed discrimination comparable to BMI, CRP, and NLR. The combined SII-BMI-CRP model showed greater discrimination with stable bootstrap internal validation. These findings support further evaluation of SII as an adjunct to clinical risk assessment, with external validation and baseline Braden Scale comparison warranted before routine use.