Observer agreement for small bowel ultrasound in Crohn’s disease: results from the METRIC trial
Gauraang Bhatnagar · Laura Quinn · Antony Higginson · Andrew Plumb · Steve Halligan · Damian Tolan · Roger Lapham · Susan Mallett · Stuart A. Taylor · METRIC study investigators
Abdom Radiol (NY). 2020 Oct;45(10):3036-3045
DOI: 10.1007/s00261-020-02405-w
Crohn’s disease (CD) is a chronic inflammatory bowel disease affecting individuals of any age that can cause significant morbidity and impact in quality of life (1). Imaging is crucial for the diagnosis and plays an essential role in the management of these patients, allowing the disease activity assessment and detection of complications. In fact, all newly diagnosed CD patients should undergo small bowel assessment, either with intestinal ultrasound (IUS), MR enterography (MRE) and/or capsule endoscopy (2).
The METRIC was a prospective multicenter cohort study comparing diagnostic accuracy, observer variability, acceptability, diagnostic impact and cost-effectiveness of MRE and IUS in newly diagnosed or relapsing CD patients (3). In the main analysis, MRE outperformed IUS in the detection, extent and activity of small bowel CD, while IUS was more sensitive in the detection of colonic disease in newly diagnosed patients (4).
In this substudy of the METRIC trial, the authors aimed to evaluate interobserver agreement for small bowel ultrasound in newly diagnosed and relapsing CD. 38 patients (11 new diagnosis and 27 relapses) were recruited from two sites. A second ultrasound examination was performed by one of a pool of six practitioners (5 radiologists and one sonographer) with variable levels of experience – ranging from 3 to 20 years of experience in gastrointestinal imaging and from 50 to >1000 small bowel ultrasound exams performed at the beginning of the trial. The presence, activity and location of small bowel and colonic disease were recorded. Comparisons were made against the reference standard (previously defined on the METRIC trial) and between practitioners. Against the reference standard, agreement for small bowel disease presence was 82% in new diagnosis and 81% in the relapsing group. For colonic disease presence the agreement was 64% in new diagnosis and 78% in relapsing group. Agreement between practitioners was 84% for small bowel and 87% for colonic disease presence.
The latest ECCO-ESGAR Guideline for the Diagnostic Assessment in IBD, published in 2019, emphasizes the role of MRE and IUS in the assessment of CD patients. CT enterography should largely be reserved for the emergency setting due to radiation exposure (2).
IUS has various advantages over MRE – it does not require oral or intravenous contrast, scanning times are faster and it is widely available. Also, while both methods are well tolerated by patients, IUS is generally preferred to MRE (5). By design, IUS is operator dependent and therefore interobserver variability has always been regarded as an important limitation. These results show that IUS evaluation in CD is reproducible and performs well against the reference standard in identifying CD presence, even amongst practitioners with different levels of experience. In this way, these results help to pave the way for wider implementation of IUS in CD in clinical practice.
On the other hand, against the reference standard, the agreement on disease activity on a per-patient basis was only fair. Although there are MRE-based disease activity scores with high accuracy, currently there are no validated scores for IUS (6,7). Further research is needed to find a reliable IUS activity index.
Finally, I would like to suggest revisiting the ESGAR-ECCO joint session during ESGAR 2019, available on the e-education portal, which I believe further enlightens the topic.
References:
- Torres J, Bonovas S, Doherty G, et al. ECCO guidelines on therapeutics in Crohn’s disease: Medical treatment. J Crohn’s Colitis. 2020;14(1):4-22. doi:10.1093/ecco-jcc/jjz180
- Maaser C, Sturm A, Vavricka SR, et al. ECCO-ESGAR Guideline for Diagnostic Assessment in IBD Part 1: Initial diagnosis, monitoring of known IBD, detection of complications. J Crohn’s Colitis. 2019;13(2):144-164. doi:10.1093/ecco-jcc/jjy113
- Taylor S, Mallett S, Bhatnagar G, et al. METRIC (MREnterography or ulTRasound in Crohn’s disease): A study protocol for a multicentre, non-randomised, single-arm, prospective comparison study of magnetic resonance enterography and small bowel ultrasound compared to a reference standard in those . BMC Gastroenterol. 2014;14(1):1-10. doi:10.1186/1471-230X-14-142
- Taylor SA, Mallett S, Bhatnagar G, et al. Magnetic resonance enterography compared with ultrasonography in newly diagnosed and relapsing crohn’s disease patients: The METRIC diagnostic accuracy study. Health Technol Assess (Rockv). 2019;23(42):vii-161. doi:10.3310/hta23420
- Miles A, Bhatnagar G, Halligan S, et al. Magnetic resonance enterography, small bowel ultrasound and colonoscopy to diagnose and stage Crohn’s disease: patient acceptability and perceived burden. Eur Radiol. 2019;29(3):1083-1093. doi:10.1007/s00330-018-5661-2
- Sturm A, Maaser C, Calabrese E, et al. Ecco-esgar guideline for diagnostic assessment in ibd part 2: Ibd scores and general principles and technical aspects. J Crohn’s Colitis. 2019;13(3):273-284E. doi:10.1093/ecco-jcc/jjy114
- Bots S, Nylund K, Löwenberg M, Gecse K, Gilja OH, D’Haens G. Ultrasound for assessing disease activity in IBD patients: A systematic review of activity scores. J Crohn’s Colitis. 2018;12(8):920-929. doi:10.1093/ecco-jcc/jjy048
Dr. João Carvalho is a fourth-year Radiology resident at the Centro Hospitalar Universitário do Porto, in Portugal. He is an active member of ESGAR and attends regularly ESGAR workshops and annual meetings.
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