American Gastroenterological Association-Proposed Fecal Calprotectin Cutoff of 50 ug/g is Associated With Endoscopic Recurrence in a Real-World Cohort of Patients With Crohn's Disease Post-ileocolic Resection.

Background: Fecal calprotectin (FC) is a reliable predictor of active bowel inflammation in postoperative Crohn's disease (CD), but cutoffs vary between studies. Recent guidelines recommend a cutoff of <50 ug/g to avoid routine endoscopy in patients at low pretest probability for CD recurrence. We evaluated the performance of this threshold in a real-world CD cohort after ileocolic resection (ICR).

Methods: In this retrospective study, patients with CD post-ICR between 2009 to 2020 with FC > 60 days but < 1 year of surgery were included from a multicenter database. Established risk factors and/or biologic prophylaxis (biologic within 90 days of surgery) defined pretest probability. Those without postoperative colonoscopy were excluded. Rates of endoscopic recurrence, defined as Rutgeerts score ≥ i2b at any time after surgery, were compared between FC < 50 versus  ≥ 50 ug/g. Student's t-test and Fisher's exact test were utilized for statistical analysis. All postoperative FCs were matched to closest colonoscopy within 1 year to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results: Thirty-seven patients categorized as either low-risk or high-risk and received biologic prophylaxis and had postoperative colonoscopy were included. Median time to first FC was 217 days (IQR 131-288). 15 (41%) patients had initial FC < 50 ug/g versus 22 (59%) ≥50 ug/g. Median time to first colonoscopy was 234 days (IQR 189-369). Compared to initial FC ≥ 50 ug/g, FC < 50ug/g experienced less endoscopic recurrence (0% vs. 36%, P = .005). Median time to first endoscopic recurrence in FC ≥ 50 ug/g was 145 days. There were 39 matched pairs of FC and colonoscopy. At an FC cutoff of 50 ug/g, calculated sensitivity was 90% and NPV was 93%, whereas specificity and PPV were 48% and 38%, respectively.

Conclusions: In this real-world cohort, FC < 50 ug/g is a useful cutoff to exclude endoscopic recurrence in a post-ICR CD population that is at low pretest probability of recurrence.