title: Diffusion-weighted Magnetic Resonance Enterography for Evaluating Bowel Inflammation in Crohn's Disease: A Systematic Review and Meta-analysis.
abstract: BACKGROUND
  To systematically determine the performance of diffusion-weighted imaging magnetic resonance enterography (DWI-MRE) for evaluating bowel inflammation in Crohn's disease and sources of heterogeneity between reported results.
  
  
  METHODS
  We identified research studies that investigated DWI-MRE to diagnose bowel inflammation (present versus absent) or to assess bowel inflammatory severity in Crohn's disease by performing a systematic search of PubMed MEDLINE and EMBASE (until March 31, 2015). Study quality was assessed using QUADAS-2. For studies reporting dichotomous diagnosis of bowel inflammation, study heterogeneity and threshold effect were analyzed, summary sensitivity and specificity were estimated, and meta-regression analysis was performed to further explore study heterogeneity. For studies reporting assessment of inflammatory severity, a qualitative summary was performed.
  
  
  RESULTS
  Of 159 articles screened, we found 12 studies (1515 bowel segments) reporting a diagnosis of bowel inflammation and 6 studies (1066 bowel segments) reporting assessment of inflammatory severity. The summary sensitivity and specificity were 92.9% (95% CI, 85.8%-96.6%; I = 87.9%) and 91% (95% CI, 79.7%-96.3%; I = 95.1%), respectively. Sensitivity and false-positive rate were inversely correlated (r = -0.650; P = 0.022). Lack of blinding to contrast-enhanced MRE when interpreting DWI-MRE (P = 0.01) and use of contrast-enhanced MRE as a reference standard (P < 0.01) in some studies were significant factors for study heterogeneity and likely caused overestimation of DWI-MRE accuracy. There was rather clear correlation between diffusion-related parameters and bowel inflammation severity, although the strengths were heterogeneous (correlation coefficient, 0.39-0.98).
  
  
  CONCLUSIONS
  DWI-MRE accuracy was very heterogeneous between studies and was likely overestimated in some studies. Despite rather clear correlation between diffusion-related parameters and bowel inflammatory severity, its strength was variable.
authors.affiliation: *Department of Radiology and the Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, South Korea; †National Evidence-based Healthcare Collaborating Agency, Jung-gu, South Korea; and ‡Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, South Korea.
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Choi
authors.forename: Kyung Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Ja Youn
authors.initials: JY
authors.lastname: Lee
authors.forename: Kyung-Jo
authors.initials: KJ
authors.lastname: Kim
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Park
mesh_terms: D003424:Crohn Disease / Q000150:complications* / Q000276:immunology / Q000503:physiopathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005069:Evaluation Studies as Topic; D006801:Humans; D007249:Inflammation / Q000175:diagnosis* / Q000209:etiology; D007422:Intestines / Q000276:immunology / Q000473:pathology*; D011379:Prognosis; D012720:Severity of Illness Index