Endoscopy is still the gold, standard for assessing disease activity in Crohn's disease (CD). Its invasiveness, poor acceptability, and cost limit its use in the era of tight control and treat-to-target management. Fecal calprotectin (FC) and intestinal ultrasound (IUS) are non-invasive alternatives to colonoscopy to assess disease activity. We aimed to evaluate the performance of IUS and FC to assess mucosal healing in CD.

All consecutive CD patients who underwent colonoscopy for mucosal healing assessment and IUS and/or FC within four weeks between September 2019 and April 2022 were included in a prospective cohort. The bowel-wall thickness (BWT) and color Doppler signal (CDS) were assessed for each segment. Endoscopic remission was defined by a CDEIS score < 3.

In total, 153 patients were included, of whom 122 showed endoscopic mucosal healing. Eighty-two (53.6 %) were female, the median was age 36 years (IQR, 28–46), and the median disease duration was 10 years (IQR, 4–19). The sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) of a BWT < 3 mm to predict endoscopic mucosal healing were 56 %, 88 %, 95 %, and 36 %, respectively (patients misclassified as mucosal healing, 2.5 %). The best FC threshold (< 92.9 µg/g) provided similar results: 77 %, 89 %, 96 %, and 67 %, respectively (patients misclassified, 2.2 %). The association of an FC < 250 µg/g with a BWT < 3 mm and the absence of CDS increased the Sp and PPV: Se 58 %, Sp 95 %, PPV 97 %, VPN 43 %; patients misclassified, 1.3 %.

Noninvasive evaluation of mucosal healing by IUS or calprotectin efficiently identifies patients with CD who have achieved endoscopic mucosal healing.