Serum ST2 in inflammatory bowel disease: a potential biomarker for disease activity.

ST2, a specific ligand of interleukin 33, was described as a biomarker protein of inflammatory processes and overexpression of ST2 in ulcerative colitis (UC) was shown previously. We aimed to investigate the potential relationship of serum ST2 levels with the clinical, endoscopic and histopathological activity scores in UC and Crohn's disease (CD). Serum ST2 levels were determined in 143 patients with inflammatory bowel disease (IBD) (83 UC and 60 CD), in 50 healthy controls (HC), and in 32 patients with irritable bowel syndrome (IBS). Serum ST2 levels were elevated in IBD (56.8 (41.9-87.2) pg/mL) compared to HC and IBS (30.7 (20.2-54.3), p<0.001 and 39.9 (25.9-68.7) pg/mL, p=0.002, respectively). No significant difference was found between UC (54.2 (41.3-93.0) pg/mL) and CD (63.8 (42.7-88.4) pg/mL) and between IBS and HC. Serum ST2 levels were significantly increased in active UC compared to inactive UC (72.5 (44.1-99.5) vs 40.0 (34.7-51.6) pg/mL, p<0.001) and in active CD in comparison with inactive CD (63.8 (42.7-88.4) vs 48.4 (29.6-56.9) pg/mL, p=0.036). Patients with CD showing fistulizing behavior had significantly higher ST2 levels compared to patients with inflammatory and stricturing CD (p<0.001). Clinical activity scores of patients with UC and CD were correlated with serum ST2 levels (r=0.692, p<0.001 and r=0.242, p=0.043, respectively). Serum ST2 levels showed stepwise increases with the increasing histopathological scores of patients with UC and CD (p<0.001 for both). The present study highlights significant associations between ST2 and IBD presence and activity and demonstrates elevated serum ST2 levels in patients with active CD as a novel finding.