A Study of the Correlation Between the Inflammatory Index and Disease Activity in Ulcerative Colitis.

Objective: To analyze the level of systemic immune-inflammatory index (SII) in patients with ulcerative colitis (UC) and assess its relationship with disease activity. Methods: This study included 616 UC patients and 211 healthy controls. Disease activity was assessed using the modified Mayo score, categorizing patients into remission (n=115) and active (n=501) groups, with the latter further stratified into mild, moderate, and severe activity. We compared multiple inflammatory indices-including SII, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), neutrophil percentage-albumin ratio (NPAR), and others-between groups. Spearman correlation and ROC curve analyses were used to evaluate their associations with disease activity and predictive value for active and severe UC. Results: SII, NLR, PLR, NPAR, and several other indices were significantly higher in the UC group than controls, while lymphocyte-to-monocyte ratio (LMR) and LHR were lower (all P<0.05). Most indices were also elevated in active versus remission UC (P<0.05), and showed significant differences across severity subgroups (P<0.05), with SII, NLR, NPAR, NHR, and MHR increasing with severity. Spearman analysis revealed positive correlations between these markers and disease activity/severity (P<0.001). ROC analysis demonstrated significant predictive value for active and severe UC (AUC>0.60, P<0.001), with NPAR exhibiting the highest efficacy (AUC=0.854). Conclusion: SII, NLR, PLR, NPAR, and other inflammatory indices are useful non-invasive biomarkers for assessing UC disease activity and severity, with NPAR showing the strongest predictive performance.