Introduction
One of the challenges in the management of inflammatory bowel disease (IBD) is the noninvasive and accurate assessment of disease activity and the prediction of treatment response and prognosis. Colonoscopy is limited due to its invasiveness; therefore, noninvasive methods are of high clinical relevance. Fecal calprotectin (FC), a surrogate marker for neutrophils, is a clinically relevant biomarker that correlates with intestinal inflammatory activity. Bowel ultrasound (B-US) is an established method that can be performed at any time and at low cost.
Aims & Methods
The aim of this study was to evaluate the correlation between B-US and FC in terms of inflammatory activity and disease severity in IBD patients. Patients were selected from a prospective study to compare FC and B-US. A total of 320 patients, including (n=188) with Crohn's disease (CD), (n=114) with ulcerative colitis (UC), and (n=18) control patients were included for further analysis. FC measurements were performed using the ELISA kit. The inflammatory activity was classified according to the FC cut-off (0: <100, 1: 100-200, 2: 200-400, 3: >400 in mg/g). The evaluation in B-US was based on the thickness of the intestinal wall (none: <2.9, mild: 3.0-4.9, moderate to severe: >5).
Results
Based on FC, patients were divided into inflammatory activity (n=211) and remission (n=109) groups. When comparing B-US and FC, there was a significant correlation regarding inflammatory activity (r=0.59, p<0.001). B-US in MC showed a better correlation (r=0.63, p<0.001) than CU (r=0.45, p<0.001) with FC. Patients with unremarkable B-US had a median FC of 57.2 mg/g (95%CI: 41.5-94.1) compared to marked inflammation in B-US median 999 mg/g (95%CI: 751.8-1517). Among patients with pathological FC values (cut-off >100 mg/g), 75.4% had sonographic evidence of inflammatory activity. Localization of inflammation in the rectum was associated with lower diagnostic accuracy. Compared to FC, B-US showed a sensitivity of 75.4%, a specificity of 78.9% and a positive predictive value of 87.4%.
Conclusion
B-US shows good diagnostic accuracy compared to FC in assessing inflammatory activity in IBD patients. Both methods can be considered as complementary non-invasive diagnostic tools in IBD.
Disclosure
Alexander Link: speakers fee: Janssen; consulting fee: Ferring.