AGA-proposed fecal calprotectin cut-off of 50ug/g is associated with endoscopic recurrence in a real-world cohort of patients with Crohn’s disease post-ileocolic resection

Abstract Intro Fecal calprotectin (FC) is a reliable predictor of active bowel inflammation in post-operative Crohn’s disease (CD), but cutoffs vary between studies. Recent guidelines recommend a cutoff of <50ug/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 pre-test 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 <50ug/g vs ≥50ug/g. Student’s t-test and Fisher’s exact test were utilized for statistical analysis. All post-operative FCs were matched to closest colonoscopy within 1 year to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results 37 patients categorized as either low-risk or high-risk and received biologic prophylaxis and had post-operative colonoscopy were included. Median time to first FC was 217 days (IQR 131 – 288). 15 (41%) patients had initial FC <50ug/g vs 22 (59%) ≥50ug/g. Median time to first colonoscopy was 234 days (IQR 189 –369). Compared to initial FC ≥50ug/g, FC<50ug/g experienced less endoscopic recurrence (0% vs 36%, p=0.005). Median time to first endoscopic recurrence in FC ≥ 50ug/g was 145 days. There were 39 matched pairs of FC and colonoscopy. At an FC cutoff of 50ug/g, calculated sensitivity was 90% and negative predictive value was 93%, whereas specificity and PPV were 48% and 38%, respectively. Conclusion In this real-world cohort, FC<50ug/g is a useful cutoff to exclude endoscopic recurrence in a post-ICR CD population that is at low pre-test probability of recurrence.