Inflammatory burden index (CRP×NLR) is associated with moderate-to-severe endoscopic activity in hospitalized patients with ulcerative colitis: a single-center retrospective study

Background In hospitalized patients with ulcerative colitis (UC), timely endoscopy may be constrained. We evaluated whether the inflammatory burden index (IBI; C-reactive protein × neutrophil-to-lymphocyte ratio [CRP×NLR]) is associated with endoscopic activity. Methods We retrospectively studied adults hospitalized with UC between 2023 and 2025 who underwent index lower endoscopy during the same admission, with blood sampling within 24 hours of admission and endoscopy within 72 hours of admission. Endoscopic activity was graded by Mayo Endoscopic Subscore (MES) and dichotomized as MES 0-1 versus ≥2. Associations with MES ≥2 were examined using logistic regression with adjustment for age, sex, and body mass index, with IBI modeled as log(IBI + 1). Discrimination was assessed by receiver operating characteristic analysis with same-sample DeLong testing. Sensitivity analyses were restricted to endoscopy within 48 hours after blood sampling. Results Among 107 patients, 83 (77.6%) had MES ≥2. IBI correlated with MES (ρ = 0.58; P < .001) and remained independently associated with MES ≥2 (adjusted OR, 5.28; 95% CI, 2.12-13.14; P < .001). Discrimination was reasonable (AUC, 0.83; 95% CI, 0.76-0.90). CRP alone performed similarly (AUC, 0.80; 95% CI, 0.71-0.88; P = .227 vs IBI), as did a CRP+NLR model (AUC, 0.84; 95% CI, 0.77-0.91; P = .40 vs IBI). Findings were directionally consistent in the ≤48-hour sensitivity analysis. The Youden-derived IBI cutoff was 3.65 (sensitivity, 72.3%; specificity, 91.7%) and should be considered exploratory. Conclusions In this cohort, IBI was associated with moderate-to-severe endoscopic activity. Performance was comparable to CRP alone, and findings should be interpreted as exploratory rather than as evidence for a standalone clinical decision tool.