Low Fecal Calprotectin Correlates with Histological Remission and Mucosal Healing in Ulcerative Colitis and Colonic Crohn's Disease

Data regarding the correlation of histologic and endoscopic healing with fecal calprotectin (FC) are conflicting. We examined how FC levels correlate with histological and endoscopic remission in colonic inflammatory bowel disease. Methods: Fifty-eight patients (23 with colonic Crohn's disease [CD] and 35 with ulcerative colitis [UC]) were included. Clinical activity was assessed by Harvey-Bradshaw index (CD) and Mayo score (UC). Inflammatory activity was assessed by ileocolonoscopy, C-reactive protein, and FC. Clinical remission was defined as Harvey-Bradshaw index ≤ 4 or Mayo score ≤ 2 and mucosal healing as Mayo endoscopic subscore = 0 (UC), and Simple Endoscopic Score-CD <3 (CD). Histologic activity was assessed in 27 patients (15 CD, 12 UC). Histological remission was defined as absence of active inflammation (Geboes score <3.1) and absence of basal plasmacytosis. Results: In UC, FC correlated with clinical Mayo score (r = 0.63, P < 0.0001). This correlation was strengthened by adding the endoscopic subscore (r = 0.90, P < 0.0001). The endoscopic subscore also independently correlated with FC (r = 0.96, P < 0.0001). In Crohn's colitis, endoscopic activity correlated with FC (r = 0.61, P < 0.001). FC levels were lower overall for patients with endoscopic remission compared with active endoscopic disease (median 100 versus 1180 g/g, P < 0.0001). FC also correlated with histological remission (Geboes score < 3.1) and absence of basal plasmacytosis in CD (r = 0.77, r = 0.80, respectively; P < 0.01). Area under the curve for FC as a predictor of histological remission (Geboes score <3.1) was 0.95 (95% CI, 0.82-1). Conclusions: Low FC correlates well with histological remission and mucosal healing in colonic inflammatory bowel disease and is thus a clinically useful surrogate for inflammatory activity.