title: 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 aged 16 and over.
abstract: BACKGROUND
  Crohn's disease (CD) is a lifelong, relapsing and remitting inflammatory condition of the intestine. Medical imaging is crucial for diagnosis, phenotyping, activity assessment and detecting complications. Diverse small bowel imaging tests are available but a standard algorithm for deployment is lacking. Many hospitals employ tests that impart ionising radiation, of particular concern to this young patient population. Magnetic resonance enterography (MRE) and small bowel ultrasound (USS) are attractive options, as they do not use ionising radiation. However, their comparative diagnostic accuracy has not been compared in large head to head trials. METRIC aims to compare the diagnostic efficacy, therapeutic impact and cost effectiveness of MRE and USS in newly diagnosed and relapsing CD.
  
  
  METHODS
  METRIC (ISRCTN03982913) is a multicentre, non-randomised, single-arm, prospective comparison study. Two patient cohorts will be recruited; those newly diagnosed with CD, and those with suspected relapse. Both will undergo MRE and USS in addition to other imaging tests performed as part of clinical care. Strict blinding protocols will be enforced for those interpreting MRE and USS. The Harvey Bradshaw index, C-reactive protein and faecal calprotectin will be collected at recruitment and 3 months, and patient experience will be assessed via questionnaires. A multidisciplinary consensus panel will assess all available clinical and imaging data up to 6 months after recruitment of each patient and will define the standard of reference for the presence, localisation and activity of disease against which the diagnostic accuracy of MRE and USS will be judged. Diagnostic impact of MRE and USS will be evaluated and cost effectiveness will be assessed. The primary outcome measure is the difference in per patient sensitivity between MRE and USS for the correct identification and localisation of small bowel CD.
  
  
  CONCLUSIONS
  The trial is open at 5 centres with 46 patients recruited. We highlight the importance of stringent blinding protocols in order to delineate the true diagnostic accuracy of both imaging tests and discuss the difficulties of diagnostic accuracy studies in the absence of a single standard of reference, describing our approach utilising a consensus panel whilst minimising incorporation bias.
  
  
  BACKGROUND
  METRIC - ISRCTN03982913 - 05.11.13.
authors.affiliation: Center for Medical Imaging, University College London, 250 Euston Rd, London NW1 2PG, UK. csytaylor@yahoo.co.uk.
authors.forename: Stuart
authors.initials: S
authors.lastname: Taylor
authors.forename: Susan
authors.initials: S
authors.lastname: Mallett
authors.forename: Gauraang
authors.initials: G
authors.lastname: Bhatnagar
authors.forename: Stuart
authors.initials: S
authors.lastname: Bloom
authors.forename: Arun
authors.initials: A
authors.lastname: Gupta
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.forename: John
authors.initials: J
authors.lastname: Hamlin
authors.forename: Ailsa
authors.initials: A
authors.lastname: Hart
authors.forename: Antony
authors.initials: A
authors.lastname: Higginson
authors.forename: Ilan
authors.initials: I
authors.lastname: Jacobs
authors.forename: Sara
authors.initials: S
authors.lastname: McCartney
authors.forename: Steve
authors.initials: S
authors.lastname: Morris
authors.forename: Nicola
authors.initials: N
authors.lastname: Muirhead
authors.forename: Charles
authors.initials: C
authors.lastname: Murray
authors.forename: Shonit
authors.initials: S
authors.lastname: Punwani
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodriguez-Justo
authors.forename: Andrew
authors.initials: A
authors.lastname: Slater
authors.forename: Simon
authors.initials: S
authors.lastname: Travis
authors.forename: Damian
authors.initials: D
authors.lastname: Tolan
authors.forename: Alastair
authors.initials: A
authors.lastname: Windsor
authors.forename: Peter
authors.initials: P
authors.lastname: Wylie
authors.forename: Ian
authors.initials: I
authors.lastname: Zealley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003362:Cost-Benefit Analysis; D003424:Crohn Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007421:Intestine, Small / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000191:economics; D008875:Middle Aged; D011446:Prospective Studies; D012008:Recurrence; D014463:Ultrasonography / Q000191:economics; D055815:Young Adult
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