THE GREY AREA: DISCREPANCIES BETWEEN IBD RISK AND COLONOSCOPY RATES AT BORDERLINE CALPROTECTIN LEVELS

Abstract BACKGROUND Fecal calprotectin is used to guide evaluation of suspected inflammatory bowel disease. However, borderline results (100-250 μg/g) can be difficult to interpret, potentially leading to unnecessary colonoscopy even when the likelihood of IBD is low. METHODS Using TriNetX, we ran a retrospective cohort study comparing 36,000 adults (18–65) with FC 100–250 μg/g and 36,000 with FC ≥ 250 μg/g. Groups were propensity score matched on age, sex, and race. We then used Kaplan–Meier survival analysis to look at new Crohn’s and ulcerative colitis diagnoses, as well as colonoscopy use over 12 months. Total colonoscopy counts between the groups were also compared. RESULTS Patients with FC 100-250 had a 48% lower risk of Crohn’s (HR 0.52, 95% CI 0.49–0.56) and 67% lower risk of ulcerative colitis (HR 0.33, 95% CI 0.31–0.36) compared to those with FC ≥ 250 μg/g. Despite this difference in disease risk, risk of colonoscopy only decreased by 11% (HR 0.89, 95% CI 0.87-0.92). This is also represented in the raw procedure count at 12,615 scopes in the borderline group and 13487 in the higher group. DISCUSSION Borderline FC values are associated with markedly lower likelihood of IBD but almost equivalent colonoscopy utilization compared to higher FC values. These findings demonstrate that imprecise use of FC thresholds may drive a disproportionate rate of unnecessary colonoscopies. Refinement of FC cutoffs and adding other risk-stratification tools could help cut down on unnecessary colonoscopies.