Prediction of disease activity of Crohn's disease through fecal calprotectin evaluated by balloon-assisted endoscopy

Background and Aim Fecal calprotectin (FC) is a useful marker for assessing the activity of intestinal inflammation. However, most studies have used ileocolonoscopy to evaluate the association of FC with intestinal inflammation, and it is not clear whether FC is useful for the evaluation of small-bowel Crohn's disease (CD). This study aimed to determine the usefulness of FC for predicting intestinal inflammation evaluated by balloon-assisted endoscopy (BAE), which can visualize the deep small intestine. Methods This was a cross-sectional, observational study involving 69 CD patients, 39 of whom had only small-bowel disease. The extended simplified endoscopic activity score for Crohn's disease (eSES-CD) was calculated based on the findings of BAE. Mucosal healing was defined as an eSES-CD of 0. Results In all CD patients, FC levels were correlated with the eSES-CD (r = 0.663, P < 0.001). The cutoff value to predict mucosal healing was 92 mg/kg, with a sensitivity of 94%, specificity of 88%, positive predictive value of 98%, negative predictive value of 64%, and the area under the curve of 0.91. Even in small-bowel CD patients, FC levels were correlated with the eSES-CD (r = 0.607, P < 0.001). The cutoff value was 92 mg/kg, with a sensitivity of 87%, specificity of 88%, positive predictive value of 96%, negative predictive value of 64%, and area under the curve of 0.85. Conclusions Fecal calprotectin showed a significant correlation with the intestinal inflammation evaluated with BAE even in patients with only small intestinal disease. FC is useful for the evaluation of CD including both the small and large intestines.