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SAT0227 Low Diagnostic Utility Of Candidate Definitions for a Positive MRi of the Spine in Axial Spondyloarthritis
  1. U. Weber1,
  2. V. Zubler2,
  3. Z. Zhao3,
  4. R. G. Lambert4,
  5. K. Rufibach5,
  6. S. M. Chan6,
  7. S. J. Pedersen7,
  8. M. Ostergaard7,
  9. W. P. Maksymowych8
  1. 1Rheumatology
  2. 2Radiology, Balgrist University Clinic, Zurich, Switzerland
  3. 3Rheumatology, PLA General Hospital, Beijing, China
  4. 4Radiology, University of Alberta, Edmonton, Canada
  5. 5rePROstat, Basel, Switzerland
  6. 6Ophthalmology, University of Alberta, Edmonton, Canada
  7. 7Rheumatology, University of Copenhagen at Glostrup, Copenhagen, Denmark
  8. 8Rheumatology, University of Alberta, Edmonton, Canada

Abstract

Background A recent consensus statement based on a systematic literature review by the Assessment of SpondyloArthritis International Society suggested the presence of ≥3 corner inflammatory lesions (CIL) or of several corner fat lesions (CFL) as candidate definitions for a positive MRI of the spine in axial spondyloarthritis (SpA) [1].

Objectives To determine data-driven cut-off values for spinal CIL and CFL yielding a specificity ≥90% and to evaluate their diagnostic utility in non-radiographic axial SpA (nr-axSpA) and ankylosing spondylitis (AS).

Methods The study sample comprised 2 independent cohorts A/B of 130 consecutive patients with back pain ≤50 years newly referred to 2 university clinics, and 20 healthy controls, in whom MRI scans of the entire spine were available. Patients were classified according to clinical examination and pelvic radiography as having nr-axSpA (n=50), AS (n=33), or non-specific back pain (NSBP; n=47). Spinal MRI were assessed by 4 blinded readers according to the standardized CanDen modules. Readers recorded bone marrow edema and fat infiltration in the central and lateral/posterior compartment of all 23 discovertebral units. We calculated cut-off values for CIL and CFL to obtain ≥90% specificity and the corresponding area under the curve (AUC) with confidence interval (CI). Finally, we tested the diagnostic utility (mean sensitivity/specificity of 4 readers) of cut-off values for spinal MRI as proposed in the literature (≥3 CIL [1] and ≥5 CFL [2]) for nr-axSpA and AS patients in both cohorts.

Results For cohorts A/B, the rounded lesion cut-offs to obtain ≥90% specificity were 3/2 CIL and 7/10 CFL, respectively. The corresponding AUC for CIL were 0.69 (CI 0.49-0.84) and 0.69 (CI 0.47-0.85) in the 2 cohorts, and for CFL 0.60 (CI 0.43-0.75) and 0.71 (CI 0.56-0.82), respectively. The diagnostic utility of the spinal thresholds of ≥3 CIL and of ≥5 CFL was low in both cohorts when comparing nr-ax SpA versus NSBP.

Diagnostic utility of 2 candidate definitions of a positive MRI of the spine in cohorts A/B

Conclusions In this controlled study, the definitions of a positive spinal MRI proposed in a recent consensus statement showed low diagnostic utility in nr-axSpA. While a cut-off of ≥2/≥3 CIL for a positive MRI was optimal, the threshold for CFL was as high as 10.

References

  1. Hermann KG et al. ARD 2012;71:1278. [2] Bennett A et al. ARD 2010;69:891.

Disclosure of Interest None Declared

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