title: Can we use structural lesions seen on MRI of the sacroiliac joints reliably for the classification of patients according to the ASAS axial spondyloarthritis criteria? Data from the DESIR cohort.
abstract: OBJECTIVE
  Investigating the utility of adding structural lesions seen on MRI of the sacroiliac joints to the imaging criterion of the Assessment of SpondyloArthritis (ASAS) axial SpondyloArthritis (axSpA) criteria and the utility of replacement of radiographic sacroiliitis by structural lesions on MRI.
  
  
  METHODS
  Two well-calibrated readers scored MRI STIR (inflammation, MRI-SI), MRI T1-w images (structural lesions, MRI-SI-s) and radiographs of the sacroiliac joints (X-SI) of patients in the DEvenir des Spondyloarthrites Indifférenciées Récentes cohort (inflammatory back pain: ≥3 months, <3 years, age <50). A third reader adjudicated MRI-SI and X-SI discrepancies. Previously proposed cut-offs for a positive MRI-SI-s were used (based on <5% prevalence among no-SpA patients): erosions (E) ≥3, fatty lesions (FL) ≥3, E/FL ≥5. Patients were classified according to the ASAS axSpA criteria using the various definitions of MRI-SI-s.
  
  
  RESULTS
  Of the 582 patients included in this analysis, 418 fulfilled the ASAS axSpA criteria, of which 127 patients were modified New York (mNY) positive and 134 and 75 were MRI-SI-s positive (E/FL≥5) for readers 1 and 2, respectively. Agreement between mNY and MRI-SI-s (E/FL≥5) was moderate (reader 1: κ: 0.39; reader 2: κ: 0.44). Using the E/FL≥5 cut-off instead of mNY classification did not change in 478 (82.1%) and 469 (80.6%) patients for readers 1 and 2, respectively. Twelve (reader 1) or ten (reader 2) patients would not be classified as axSpA if only MRI-SI-s was performed (in the scenario of replacement of mNY), while three (reader 1) or six (reader 2) patients would be additionally classified as axSpA in both scenarios (replacement of mNY and addition of MRI-SI-s). Similar results were seen for the other cut-offs (E≥3, FL≥3).
  
  
  CONCLUSIONS
  Structural lesions on MRI can be used reliably either as an addition to or as a substitute for radiographs in the ASAS axSpA classification of patients in our cohort of patients with short symptom duration.
authors: Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.
authors: Pauline A C
authors: PA
authors: Bakker
authors: Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.
authors: Rosaline
authors: R
authors: van den Berg
authors: Department of Rheumatology, Clinique Hartmann, Neuilly sur Seine, France.
authors: Gregory
authors: G
authors: Lenczner
authors: Department of Radiology B, Paris Descartes University, Cochin Hospital, Paris, France.
authors: Fabrice
authors: F
authors: Thévenin
authors: Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors: Monique
authors: M
authors: Reijnierse
authors: Department of Rheumatology, Hôpital Albert Chenevier, Henri Mondor, Créteil, France.
authors: Pascal
authors: P
authors: Claudepierre
authors: Department of Rheumatology, Université de Franche-Comté, Besancon, France.
authors: Daniel
authors: D
authors: Wendling
authors: Department of Rheumatology, Hôpital Cochin, Paris, France.
authors: Maxime
authors: M
authors: Dougados
authors: Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.
authors: Désirée
authors: http://orcid.org/0000-0002-5781-158X
authors: D
authors: van der Heijde
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005602:France; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D011446:Prospective Studies; D011859:Radiography; D015203:Reproducibility of Results; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D058566:Sacroiliitis / Q000000981:diagnostic imaging*; D025241:Spondylarthritis / Q000145:classification / Q000000981:diagnostic imaging; D013167:Spondylitis, Ankylosing / Q000145:classification / Q000000981:diagnostic imaging*
keywords: Ankylosing Spondylitis; Low Back Pain; Magnetic Resonance Imaging; Spondyloarthritis