title: The diagnostic utility of magnetic resonance imaging in spondylarthritis: an international multicenter evaluation of one hundred eighty-seven subjects.
abstract: OBJECTIVE
  To systematically assess the diagnostic utility of magnetic resonance imaging (MRI) to differentiate patients with spondylarthritis (SpA) from patients with nonspecific back pain and healthy volunteers, using a standardized evaluation of MR images of the sacroiliac joints.
  
  
  METHODS
  Five readers blinded to the patients and diagnoses independently assessed MRI scans (T1-weighted and STIR sequences) of the sacroiliac joints obtained from 187 subjects: 75 patients with ankylosing spondylitis (AS; symptom duration ≤ 10 years), 27 patients with preradiographic inflammatory back pain (IBP; mean symptom duration 29 months), 26 patients with nonspecific back pain, and 59 healthy control subjects; all participants were age 45 years or younger. Bone marrow edema, fat infiltration, erosion, and ankylosis were recorded according to standardized definitions using an online data entry system. We calculated sensitivity, specificity, and positive and negative likelihood ratios (LRs) for the diagnosis of SpA based on global assessment of the MRI scans.
  
  
  RESULTS
  Diagnostic utility was high for all 5 readers, both for patients with AS (sensitivity 0.90, specificity 0.97, positive LR 44.6) and for patients with preradiographic IBP (sensitivity 0.51, specificity 0.97, positive LR 26.0). Diagnostic utility based solely on detection of bone marrow edema enhanced sensitivity (67%) for patients with IBP but reduced specificity (88%); detection of erosions in addition to bone marrow edema further enhanced sensitivity (81%) without changing specificity. A single lesion of the sacroiliac joint on MRI was observed in up to 27% of control subjects.
  
  
  CONCLUSIONS
  This systematic and standardized evaluation of sacroiliac joints in patients with SpA showed that MRI has much greater diagnostic utility than has been documented previously. We present for the first time a data-driven definition of MRI-visualized positivity for SpA.
authors.affiliation: 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: Mikkel
authors.initials: M
authors.lastname: Østergaard
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
authors.forename: Susanne J
authors.initials: SJ
authors.lastname: Pedersen
authors.forename: Walter P
authors.initials: WP
authors.lastname: Maksymowych
mesh_terms: D000328:Adult; D001416:Back Pain; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D012446:Sacroiliac Joint; D012680:Sensitivity and Specificity; D025241:Spondylarthritis / Q000175:diagnosis*; D055815:Young Adult