Serum Interleukin-10 as a Potential Biomarker for Deep Remission and Histologic Activity in Ulcerative Colitis

Background/Objectives: Deep remission, defined as the coexistence of endoscopic remission and histologic healing, has emerged as an advanced therapeutic target in ulcerative colitis (UC). However, reliable non-invasive biomarkers capable of accurately reflecting histologic inflammatory status remain limited. We aimed to evaluate the association between serum interleukin-10 (IL-10) concentrations and deep remission in UC and to assess its discriminatory performance. Methods: In this prospective single-center observational study, consecutive adult patients with ulcerative colitis undergoing clinically indicated colonoscopy were enrolled. Serum IL-10 concentrations were measured prior to endoscopy using an enzyme-linked immunosorbent assay. Histologic healing was defined as a Geboes score < 2.0, and deep remission as the coexistence of endoscopic remission and histologic healing. Associations were evaluated using Firth penalized logistic regression. Discrimination was assessed using receiver operating characteristic analysis with bootstrap internal validation (500 resamples). Results: Among 44 patients, 18 (40.9%) achieved deep remission. Serum IL-10 levels were significantly higher in patients with histologic healing compared with those with active histologic inflammation (p < 0.001). Log-transformed IL-10 was independently associated with deep remission in both univariable and multivariable models. The primary multivariable model demonstrated apparent good discrimination (apparent AUC 0.88; optimism-corrected AUC 0.85). Among patients in endoscopic remission, non-detectable IL-10 identified persistent histologic activity with high sensitivity (92.9%) and negative predictive value (94.4%), although these findings are exploratory. Conclusions: Serum IL-10 concentrations were independently associated with deep remission and showed potentially promising internally validated discriminatory performance within this cohort. These findings are hypothesis-generating and require external validation in larger cohorts before clinical application.