Introduction. Crohn's disease (CD) is a chronic inflammatory bowel disease (IBD) with periods of remission and exacerbation. Numerous studies have been conducted in order to identify the ideal marker when it comes to the inflammatory bowel diseases. In the literature, fecal calprotectin is mentioned as a marker of inflammation. Elevated levels of calprotectin can be detected in stool and they indicate the migration of neutrophils to the intestinal mucosa that occurs with intestinal inflammation. 
The aim. The main goal of this study was to examine the concentration of fecal calprotectin and CRP depending on the clinical, endoscopic and histological characteristics of patients with Crohn's disease and whether there is a correlation of these markers with disease activity.
Methods. The research was conducted in the period from January 2015 to January 2016. The study included subjects who had been diagnosed with Crohn's disease. The study involved 45 respondents, aged 20 - 58 years. All subjects included in the study underwent a colonoscopic examination with biopsy and pathohistological analysis. Fecal calprotectin was determined in one stool sample in all subjects, and that was done quantitatively by a commercial ELISA assay. Determination of serum CRP concentrations was performed in the Central Biochemical Laboratory by standard methods.
Results. Fecal concentrations of calprotectin are elevated in all three forms of the disease, while they are significantly higher in moderately severe (545 vs. 218, p ˂ 0.001) and severe forms of the disease (1000 vs. 218, p ˂ 0.001) compared to the mild form. Fecal concentrations of calprotectin are significantly higher at endoscopic grade 3 compared to the other three endoscopic grades (765.3 vs. 314, p ˂ 0.001), (765.3 vs. 392.8, p ˂ 0.001), (765.3 vs. 448.2, p ˂ 0.001). Fecal concentrations of calprotectin are significantly higher in extensive pathological findings compared to normal epithelial surface (1000 vs. 21, p ˂ 0.001) as well as in extensive pathological findings compared to focal pathological findings (1000 vs. 309, p ˂ 0.001).
Conclusion. The more severe form of clinical disease activity is accompanied by higher fecal values of calprotectin and higher endoscopic grade, and a more severe histological grade of disease is accompanied by higher fecal values of calprotectin.

 Keywords: Crohn's disease, fecal calprotectin, C-reactive protein, disease activity

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Mladen Maksić