Fecal Calprotectin in Ileal Crohn's Disease: Relationship with Magnetic Resonance Enterography and a Pathology Score.

Background: Magnetic resonance enterography (MRE) is an effective method of assessing small bowel Crohn's disease (CD). Fecal calprotectin (FC) correlates well with endoscopic disease activity. We aimed to evaluate the correlation between FC and disease activity according to MRE and surgical pathology in small bowel CD.

Methods: One hundred twenty consecutive patients with ileal CD who underwent MRE assessment were included. Clinical data, C-reactive protein and FC, radiological and histological variables were obtained. Clinical activity was evaluated by the Harvey-Bradshaw Index and FC by enzyme-linked immunosorbent assay. MRE activity was assessed by means of the Magnetic Resonance Index of Activity score. Chiorean's score was used to grade pathological inflammation in surgical specimens.

Results: Seventy-five patients (62.5%) were in clinical remission (Harvey-Bradshaw Index < 5) and 45 (37.5%) had active disease (Harvey-Bradshaw Index ≥ 5). The Magnetic Resonance Index of Activity score was significantly associated with FC levels (P < 0.01), with a moderate overall correlation (Spearman's r = 0.56, P < 0.001). FC reflected MRE inflammatory activity with an area under the receiver operating characteristic curve of 0.914 (confidence interval, 0.849-0.958; P < 0.001). A cutoff value of 166.50 μg/g had 90% sensitivity, 74% specificity, 89% positive predictive value, and 76% negative predictive value for diagnosis of inflammation. Twenty-eight of 120 patients were operated. Surgical pathology showed a good agreement with FC for moderate (P = 0.03) and severe (P = 0.01) Chiorean's index. No relationship was detected for C-reactive protein.

Conclusions: FC correlates with the degree of MRE inflammatory activity and with surgical pathology damage in ileal CD. Thus, FC could be a surrogate marker of disease control used to select patients for MRE assessment and therapeutic adjustment.