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Does spinal MRI add incremental diagnostic value to MRI of the sacroiliac joints alone in patients with non-radiographic axial spondyloarthritis?
  1. Ulrich Weber1,2,
  2. Veronika Zubler3,
  3. Zheng Zhao4,
  4. Robert GW Lambert5,
  5. Stanley M Chan6,
  6. Susanne J Pedersen7,
  7. Mikkel Østergaard7,
  8. Kaspar Rufibach8,
  9. Walter P Maksymowych1
  1. 1Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
  2. 2Department of Rheumatology, Balgrist University Hospital, Zurich, Switzerland
  3. 3Department of Radiology, Balgrist University Hospital, Zurich, Switzerland
  4. 4Department of Rheumatology, PLA General Hospital, Beijing, China
  5. 5Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada
  6. 6Department of Ophthalmology, University of Alberta, Edmonton, Alberta, Canada
  7. 7Copenhagen Center for Arthritis Research, Center for Rheumatology and Spinal Diseases, University of Copenhagen, Copenhagen, Denmark
  8. 8Rufibach rePROstat, Biostatistical Consulting and Training, Basel, Switzerland
  1. Correspondence to Dr Ulrich Weber, Division of Rheumatology, Department of Medicine, University of Alberta, 562 Heritage Medical Research Building, Edmonton, Alberta, Canada T6G 2S2; ulrich.weber02{at}


Objective To assess the incremental diagnostic value of spine MRI evaluated separately from and combined with sacroiliac joint (SIJ) MRI in non-radiographic axial spondyloarthritis (nr-axSpA) compared with SIJ MRI alone.

Methods The study sample comprised two independent cohorts A/B of 130 consecutive patients aged ≤50 years with back pain, newly referred to two university clinics, and 20 healthy controls. Patients were classified according to clinical examination and pelvic radiographs as having nr-axSpA (n=50), ankylosing spondylitis (n=33), or non-specific back pain (n=47). Four readers assessed SIJ and spine MRI separately 6 months apart, and 1–12 months later both scans simultaneously using standardised modules. Readers recorded presence/absence of SpA and their level of confidence in this conclusion on a 0–10 scale (0=definitely not; 10=definite). We analysed differences between SIJ MRI versus spine MRI alone, and SIJ MRI alone versus combined MRI, descriptively by the number/percentage of subjects according to the mean of four readers.

Results In cohorts A/B, 15.8%/24.2% of patients with nr-axSpA having a negative SIJ MRI were reclassified as being positive for SpA by global evaluation of combined scans. However, 26.8%/11.4% of non-specific back pain controls and 17.5% of healthy volunteers with a negative SIJ MRI were falsely reclassified as having SpA by combined MRI. Low confidence in a diagnosis of SpA by SIJ MRI increased to high confidence by combined MRI in 6.6%/7.3% of patients with nr-axSpA.

Conclusions Combined spine and SIJ MRI added little incremental value compared with SIJ MRI alone for diagnosing patients with nr-axSpA and enhancing confidence in this diagnosis.

  • Spondyloarthritis
  • Magnetic Resonance Imaging
  • Ankylosing Spondylitis

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