Fecal calprotectin is a reliable marker of endoscopic response to vedolizumab therapy: A simple algorithm for clinical practice

Background and aim: The association of fecal calprotectin (FC) and endoscopic response in inflammatory bowel disease patients during vedolizumab (VDZ) treatment is largely unknown. The aim of this study is to assess the diagnostic value of FC to predict endoscopic response.

Methods: Patients with active endoscopic disease at baseline were included. Endoscopies and FC tests were performed at baseline and week 16. Patients with a confirmed endoscopic response at week 16 continued VDZ maintenance therapy, and endoscopy and FC tests were performed at week 52. Endoscopic response was defined as endoscopic Mayo score reduction of ≥ 1, SES-CD of ≥ 50%, or Rutgeerts' score of ≥ 1. Correlations were assessed using Spearman and receiver operating characteristic statistics.

Results: A total of 114 patients, 46 ulcerative colitis and 68 Crohn's disease patients (44 men, median age 40 years), were included after the start of VDZ; 85% was anti-tumor necrosis factor alpha refractory. Endoscopic response was observed in 60 (53%) patients at week 16; the response sustained in 73% at week 52. FC decreased significantly from 819 at baseline to 154 μg/g at week 16. FC at weeks 16 and 52 were significantly correlated to (sustained) endoscopic response (r = -0.62 / r = -0.67, P < 0.001). FC < 200 μg/g indicates endoscopic response (area under the curve = 0.89, positive predictive value = 94%), whereas FC > 450 μg/g indicates endoscopic non-response after induction (negative predictive value = 83%). An increase in FC level of > 400 μg/g after induction indicates endoscopic loss of response (area under the curve = 0.97, negative predictive value = 96%).

Conclusion: This prospective study demonstrates a significant correlation between FC and endoscopic response to VDZ. FC < 200 μg/g prognosticate endoscopic response, and FC > 450 μg/g endoscopic non-response. An increase in FC of > 400 μg/g after induction indicates endoscopic loss of response. This simple FC algorithm may guide clinical decisions on the continuation and optimization of VDZ in inflammatory bowel disease patients.