title: Assessment of structural lesions in sacroiliac joints enhances diagnostic utility of magnetic resonance imaging in early spondylarthritis.
abstract: OBJECTIVE
  To compare the diagnostic utility of T1-weighted and STIR magnetic resonance imaging (MRI) sequences in early spondylarthritis (SpA) using a standardized approach to the evaluation of sacroiliac (SI) joints, and to test whether systematic calibration of readers directed at recognition of abnormalities on T1-weighted MRI would enhance diagnostic utility.
  
  
  METHODS
  Six readers independently assessed T1-weighted and STIR MRI scans of the SI joints from 187 subjects: 75 ankylosing spondylitis (AS) and 27 preradiographic inflammatory back pain (IBP) patients, and 26 mechanical back pain and 59 healthy volunteer controls ages ≤45 years. The exercise was repeated 6 months later on a random selection of 30 AS patients and 34 controls after calibration directed at lesions visible on T1-weighted MRI. Specific MRI lesions were recorded according to standardized definitions. In addition to deciding on the presence/absence of SpA, readers were asked which MRI sequence and which type of lesion was the primary basis for their diagnostic conclusion.
  
  
  RESULTS
  Structural lesions were detected in 98% of AS patients and 64% of IBP patients. A diagnosis of SpA was based on T1-weighted or combined T1-weighted/STIR sequences in 82% of AS patients and 41% of IBP patients. Calibration enhanced the diagnostic utility of MRI in the majority of readers, especially those considered less experienced; the mean positive and negative likelihood ratios (of 6 readers) were 14.5 and 0.08 precalibration, respectively, and 22.2 and 0.02 postcalibration, respectively.
  
  
  CONCLUSIONS
  Recognition of structural lesions on T1-weighted MRI contributes significantly to its diagnostic utility in early SpA. Rheumatologist training directed at detection of lesions visible on T1-weighted MRI enhances diagnostic utility.
authors.affiliation: Department of Rhuematology, Balgrist University Hospital, Zurich, Switzerland. ulrich.weber@balgrist.ch
authors.forename: Ulrich
authors.initials: U
authors.lastname: Weber
authors.forename: Robert G W
authors.initials: RG
authors.lastname: Lambert
authors.forename: Susanne J
authors.initials: SJ
authors.lastname: Pedersen
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
authors.forename: Mikkel
authors.initials: M
authors.lastname: Østergaard
authors.forename: Walter P
authors.initials: WP
authors.lastname: Maksymowych
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012446:Sacroiliac Joint / Q000473:pathology*; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000175:diagnosis*