Level of Fecal Calprotectin Correlates With Severity of Small Bowel Crohn's Disease, Measured by Balloon-assisted Enteroscopy and Computed Tomography Enterography

Background & aims: Previous studies have not found a correlation between fecal level of calprotectin and small bowel Crohn's disease (CD). However, these studies evaluated patients mainly by ileocolonoscopy, which views up to only the terminal ileum rather than entire small intestine. We investigated whether level of fecal calprotectin (FC) is a marker of active CD of the small bowel, identified by balloon-assisted enteroscopy and computed tomography enterography (CTE).

Methods: We performed a prospective study of 123 patients with CD (35 with ileitis, 72 with ileocolitis, and 16 with colitis) evaluated by balloon-assisted enteroscopy from May 2012 through July 2015 at Toho University Sakura Medical Centre in Japan. Patients with strictures detected by balloon-assisted enteroscopy were evaluated by CTE (n = 17). Fecal samples were collected from each patient, and levels of calprotectin were measured; patient demographic variables and medical history were also collected. We developed a CTE scoring system for disease severity that was based on bowel wall thickness, mural hyperenhancement, and engorged vasa recta. The association between level of FC and simple endoscopic index for CD score or CTE was evaluated by using Spearman rank correlation coefficient.

Results: Level of FC correlated with the simple endoscopic index for CD score (r = 0.6362, P < .0001), even in patients with only active disease of the small intestine (r = 0.6594, P = .0005). In the 17 patients with strictures that could not be passed with the enteroscope, CTE detected all lesions beyond the strictures as well as areas in the distal side of the strictures. Level of FC correlated with CTE score in these patients (r = 0.4018, P = .0011, n = 63). In receiver operating characteristic analyses, the FC cutoff value for mucosal healing was 215 μg/g; this cutoff value identified patients with healing with 82.8% sensitivity, 71.4% specificity, positive predictive value of 74.3%, negative predictive value of 80.6%, odds ratio of 12.0, and area under the receiver operating characteristic curve value of 0.81.

Conclusions: A combination of measurement of level of FC and CTE appears to be effective for monitoring CD activity in patients with small intestinal CD, including patients with strictures that cannot be passed by conventional endoscopy.