PROGNOSTIC VALUE OF FECAL MARKERS IN THE DIAGNOSIS OF AXIAL SPONDYLOARTHRITIS ASSOCIATED WITH CROHN’S DISEASE

Introduction. Spondyloarthritis is presented by various chronic diseases, including classical axial spondyloarthritis and spondyloarthritis associated with inflammatory bowel diseases, particularly Crohn’s disease. Diagnosis of the latter one may be difficult due to chronic subclinical intestinal inflammation in classic axial spondyloarthritis characterized by the increased fecal calprotectin levels in 40-70% of cases. Gut eosinophilic inflammation to be detected by fecal eosinophilic neurotoxin plays an important role in the Crohn’s disease pathogenesis. Aim. To examine differences in the fecal calprotectin and eosinophilic neurotoxin concentrations in patients with axial spondyloarthritis, Crohn’s disease, and their combination and to establish the significance of biomarkers in the differential diagnosis of classical and Crohn’s disease-associated axial spondyloarthritis. Materials and Methods. 16 patients with axial spondyloarthritis associated with Crohn’s disease (group A), 29 patients with axial spondyloarthritis (group B), and 25 patients with Crohn’s disease (group C) were examined. Calprotectin and eosinophil-derived neurotoxin in feces were studied by enzyme-linked immunosorbent assay. Statistical analysis was carried out using nonparametric criteria, logistic regression, and ROC-curve. Results and Discussion. A statistically significant increase in the median concentrations of fecal calprotectin (Kruskal-Wallis criterion – 8.624; p – 0.013) and eosinophil-derived neurotoxin (Kruskal-Wallis criterion – 6.605; p – 0.037) was found in group A. For both fecal markers, the differences were significant as compared to patients from group B (fecal calprotectin: U-test – 13.395; p – 0.026; eosinophil-derived neurotoxin: U-test – 11.406; p – 0.038). The value of calprotectin in stool of 177.28 μg/g and above have allowed to correctly classify patients of groups A and B in 76.2% of cases, and the level of eosinophilic neurotoxin of 0.745 μg/g and above – in 78.6% of cases; the area under the ROC-curve has been 0.903 (p – 0.001) for fecal calprotectin and 0.882 (p – 0.002) for eosinophil-derived neurotoxin. Combined model with fecal calprotectin 120.32 μg/g and above and eosinophil-derived neurotoxin 0.700 μg/g and above have had an accuracy of 84.0% (sensitivity – 87.5%, specificity – 77.8%). Conclusions. A combined study of fecal calprotectin and eosinophil-derived neurotoxin with the cut-off levels of 120.32 μg/g and 0.700 μg/g, respectively, allows differentiating Crohn’s disease-associated and classical axial spondyloarthritis more accurately than an isolated assessment of these markers.