Intestinal Ultrasonography as an Alternative to Fecal Calprotectin to Monitor Patients with Crohn's Disease: Experience from a Novice Sonographer

Background: While fecal calprotectin (Fcal) is now recommended, the positioning of intestinal ultrasonography (IUS) is still unknown to monitor patients with CD.

Aims: To assess the agreement between IUS performed by a novice sonographer and Fcal to detect active CD and to compare these two monitoring tools to determine the need for therapeutic escalation.

Methods: In this cross-sectional prospective study, we consecutively included CD patients ≥ 18 years-old with concomitant IUS and Fcal testing within 7 days. IUS was performed by a novice sonographer. The endpoints were the agreement between IUS and Fcal (> 150 µg/g) to detect active CD and the need for therapeutic escalation.

Results: Among 66 patients undergoing IUS, 56 patients had also Fcal testing. The agreement between IUS and Fcal to detect an active CD was 80.4% (κ-coefficient = 0.536 ± 0.127). Fcal, IUS or both had respectively the following positive (76.9%[54.0-99.8], 70.0%[49.9-90.1], and 81.8%[59.0-100.0]) and negative (81.4%[69.8-93.0], 88.9%[78.6-99.2], and 80.0%[68.3-91.7]) predictive values to detect active CD requiring therapeutic escalation. Using a 10 points-acceptability numerical scale, IUS presented with a better acceptability than Fcal (9.5 ± 1.2 vs 8.0 ± 2.3, p < 0.0001). Contrary to the agreement with Fcal and the performances of IUS to identify the need for therapeutic escalation, the duration of IUS procedure decreased over time (correlation coefficient = - 0.54, p = 0.001) and plateaued between 15 and 20 min-long from the 24th procedure.

Conclusion: IUS and fecal calprotectin do not give the same information and could be complementary to monitor patients with CD.