Zhengyu Ren,1,* Zhewei Zhang,2,* Haichen Li,1 Pumeng Fu,1 Ruixue Wang,1 Siyao Wang,1 Yingchao Li1 

1Department of Gastroenterology, First Affiliated Hospital, Xi’an Jiaotong University, Shaanxi, People’s Republic of China; 2Department of PET-CT Center, First Affiliated Hospital, Xi’an Jiao Tong University, Shaanxi, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Yingchao Li, Email liyingchao@xjtufh.edu.cn

Purpose: Ulcerative colitis (UC) requires new non-invasive serum biomarkers for assistance in monitoring due to the low rate of endoscopic follow-up. Previous research indicated reduced levels of serum indirect bilirubin (sIBIL), serum total bilirubin (sTBIL), and serum total bile acids (sTBAs) in UC patients. This study aims to assess their monitoring potential in UC during biologic therapy.
Methods: We conducted a retrospective single-center study including 138 UC patients and 150 controls with normal colonoscopy results. The receiver operating characteristic (ROC) curve was used to assess diagnostic value of sIBIL, sTBIL, and sTBAs. Spearman correlation analysis was performed to assess the association between these biomarkers and the severity of both endoscopic findings and clinical symptoms in UC patients. Additionally, changes in serum biomarkers were analyzed in 72 UC patients during biologic therapy, with stratified analyses based on endoscopic remission status.
Results: Patients with UC exhibited lower concentrations of sIBIL, sTBIL, and sTBAs compared to the controls (P < 0.05), and all these biomarkers demonstrated moderate diagnostic value in identifying UC from normal controls (P < 0.05). sIBIL concentration negatively correlated with disease severity and showed a progressive increase during biologic therapy, particularly in patients achieving endoscopic remission at week 52 (P < 0.05). The sIBIL concentration in the remission group was significantly higher than that in the non-remission group after week 26 (P < 0.05). For sTBAs, concentration initially increased and then decreased, with a turning point at week 14 in the remission group (P < 0.05) and at week 26 in the non-remission group (P > 0.05). No significant differences in sTBAs concentrations were found between remission and non-remission groups at any time (P > 0.05).
Conclusion: sIBIL may be used as a valuable serum biomarker for the clinical diagnosis and the monitoring of response to biologics. Additionally, the change trend of sTBAs may provide reference value for monitoring UC biologic therapy. However, further studies are needed to analyze the changes in its internal composition.

Keywords: ulcerative colitis, serum total bilirubin, serum indirect bilirubin, serum total bile acids, endoscopic remission