Research Article: Observer agreement for small bowel ultrasound in Crohn’s disease: results from the METRIC trial

Date Published: February 10, 2020

Publisher: Springer US

Author(s): Gauraang Bhatnagar, Laura Quinn, Antony Higginson, Andrew Plumb, Steve Halligan, Damian Tolan, Roger Lapham, Susan Mallett, Stuart A. Taylor.


To prospectively evaluate interobserver agreement for small bowel ultrasound (SBUS) in newly diagnosed and relapsing Crohn’s disease.

A subset of patients recruited to a prospective trial comparing the diagnostic accuracy of MR enterography and SBUS underwent a second SBUS performed by one of a pool of six practitioners, who recorded the presence, activity and location of small bowel and colonic disease. Detailed segmental mural and extra-mural observations were also scored. Interobserver variability was expressed as percentage agreement with a construct reference standard, split by patient cohort, grouping disease as present or absent. Prevalence adjusted bias adjusted kappa (PABAK), and simple percentage agreement between practitioners, irrespective of the reference standard, were calculated.

Thirty-eight patients (11 new diagnosis, 27 relapse) were recruited from two sites. Overall percentage agreement for small bowel disease presence against the consensus reference was 82% (52–95% (95%CI)), kappa coefficient (κ) 0.64, (substantial agreement) for new diagnosis and 81%, κ 0.63 (substantial agreement) for the relapsing cohort. Agreement for colonic disease presence was 64%, κ 0.27 (fair agreement) in new diagnosis and 78%,κ 0.56 (moderate agreement) in the relapsing cohort. Simple agreement between practitioners was 84% and 87% for small bowel and colonic disease presence respectively. Practitioners agreed on small bowel disease activity in 24/27 (89%) where both identified disease. Kappa agreement for detailed mural observations ranged from κ 0.00 to 1.00.

There is substantial practitioner agreement for small bowel disease presence in newly diagnosed and relapsing CD patients, supporting wider dissemination of enteric US.

The online version of this article (10.1007/s00261-020-02405-w) contains supplementary material, which is available to authorized users.

Partial Text

Meta-analyses suggest that small bowel ultrasound (SBUS) achieves a high sensitivity for the presence and extent of small bowel Crohn’s disease (CD), recently confirmed in a prospective multicentre trial setting by the METRIC trial [1–4]. SBUS has several advantages over Magnetic resonance enterography (MRE). It does not require oral or intravenous contrast and is preferred by patients [5]. Furthermore, it is widely available and can be employed at both bedside and out-patient clinic [6].

We report substantial sonographic agreement for the presence of small bowel CD, both in newly diagnosed patients and those suspected of luminal relapse. Agreement for colonic disease presence was substantial in the relapse cohort and fair for new diagnoses. Agreement for small bowel and colonic disease extent (i.e. presence and segmental location) was inferior to that for disease presence alone.




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