Association of serum interleukin-6 and soluble interleukin-2-receptor levels with disease activity status in patients with inflammatory bowel disease: A prospective observational study

Crohn's disease (CD) and ulcerative colitis (UC) are characterized by overexpression of proinflammatory cytokines. We determined the association of serum levels of interleukin (IL)-6, soluble -IL-2-receptor (sIL-2R) and CRP as well as of faecal calprotectin (FC) values with disease activity in CD and UC patients. This prospective study included 145 CD and 84 UC patients. Serum proinflammatory biomarkers and FC levels were measured and demographic, clinical and endoscopic characteristics were collected. Uni- and multivariate statistical analyses were performed. Serum IL-6 and CRP levels as well as FC values of CD patients were associated with clinical and endoscopic remission. In multivariate analysis serum IL-6 levels remained significantly associated with clinical and endoscopic remission. FC levels were also associated with endoscopic remission in CD patients. CD patients under the threshold levels of 8.5 pg/mL and 5.5 pg/mL for serum IL-6 were in 70% and 66% in clinical and endoscopic remission, respectively. Serum sIL-2R, CRP levels and FC values of UC patients were associated in univariate analysis with clinical and endoscopic remission. In multivariate analysis CRP and FC values were associated with clinical remission and serum sIL-2R as well as FC levels with endoscopic remission. UC patients under the threshold levels of 759 IU/mL and 646 IU/mL for serum sIL-2R were in 76% and 76% in clinical and endoscopic remission, respectively. Beside CRP and FC, serum IL-6 levels in CD patients and sIL-2R levels in UC patients can be a further useful non-invasive biomarker to identify the disease activity status.