Serum YKL-40 as a marker of disease activity and stricture formation in patients with Crohn's disease

Background and Aim: YKL-40 is secreted by macrophages and neutrophils and is a growth factor for vascular endothelial cells and fibroblasts. Elevated serum levels of YKL-40 have been reported in patients with various inflammatory conditions and ongoing fibrosis. The aim of this study was to investigate the relationship between serum concentrations of YKL-40 and disease activity, acute phase reactants, and the presence of strictures in patients with Crohn's disease (CD). Methods: We studied the serum concentrations of YKL-40 in 41 patients with CD, in which 12 had an endoscopically- or radiologically-proven stricture formation. Forty-six age- and sex-matched healthy volunteers served as controls and a multivariate regression analysis was performed to find out the independent predictors of intestinal strictures and clinical activity. Results: The serum YKL-40 concentrations in the patients were significantly higher than that in the healthy controls (105.69 +/- 88.08 ng/mL [range 20.23-333.57] vs 44.92 +/- 24.89 ng/mL [range 18.31-113.43], P = 0.000) and patients with a stricture formation had significantly higher YKL-40 levels than those without strictures (167.50 +/- 119.30 ng/mL [range 23.62-333.57] vs 80.12 +/- 56.38 ng/mL [range 20.23-259.19], P = 0.003). Significant correlations were noted between YKL-40 levels and clinical activity (r = 0.681; P = 0.000) and the presence of intestinal strictures (r = 0.457; P = 0.003). The multivariate regression analysis found the serum YKL-40 levels to be an independent predictor of intestinal strictures (P = 0.001) and clinical activity (P = 0.001). Conclusion: Patients with CD, particularly those with a stricture formation, have significantly higher levels of YKL-40. YKL-40 seems to be a useful marker of disease activity as well as stricture formation in patients with CD.