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SAT0243 Influence of Taking Structural Lesions into Account in Addition to Inflammatory Lesions on MRI of the Sacroiliac Joints On The Classification of Patients with Possible Axial Spondyloarthritis
  1. R. van den Berg1,
  2. M. de Hooge1,
  3. F. van Gaalen1,
  4. V. Navarro Compán1,
  5. M. Reijnierse2,
  6. K. Fagerli3,
  7. R. Landewé4,
  8. M. van Oosterhout5,
  9. L. Punzi6,
  10. T. Huizinga1,
  11. D. van der Heijde1
  1. 1Rheumatology
  2. 2Radiology, LUMC, Leiden, Netherlands
  3. 3Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  4. 4Clinical Immunology and Rheumatology, AMC, Amsterdam
  5. 5Rheumatology, GHZ, Gouda, Netherlands
  6. 6Rheumatology, University of Padova, Padova, Italy

Abstract

Background The ASAS definition of a positive MRI of the sacroiliac joints (MRI-SI+) for the classification of axial spondyloarthritis (axSpA) patients (pts) includes inflammatory lesions only1,2. The role of structural lesions (SL) on MRI-SI in classifying pts is unclear1.

Objectives To explore the potential role of SL on MRI-SI in classifying axSpA pts.

Methods Pts with back pain (≥3 months, ≤2 years, onset <45 years) from the 5 centers in the SPondyloArthritis Caught Early (SPACE)-cohort were included. Pts underwent MRI-SI. MRIs-SI were scored by 3 well-calibrated readers independently for ankylosis, sclerosis, erosions, and fatty lesions (FL) (T1-weighted images; STIR viewed simultaneously). Erosions, sclerosis and FL were defined according to the MORPHO definition3 (≥1 lesion on ≥2 consecutive slices or ≥2 lesion on 1 slice). Ankylosis was defined as ≥1 lesion on ≥1 slice. Lesions were considered present if 2/3 readers agreed. MRI was considered positive for several (combinations of) SL (MRI-SI-s+) using cut-offs based on the acceptance of ≤5% false-positives in pts without SpA. Pts are considered as possible axSpA if not fulfilling the ASAS axSpA criteria3, but if ≥1 specific SpA-feature (high LR+) or ≥2 less specific SpA-features are present4. We classified possible axSpA pts using MRI-SI-s+ instead of MRI-SI+ and calculated the LR product with LR+ 9.0 for MRI-SI-s+ as if MRI-SI+4. Based on the LR product the probability of having axSpA was calculated4.

Results Only possible axSpA pts with MRI-SI data were included (n=116). Depending on the used MRI-SI-s+ definition, 1% (ankylosis ≥1) to 6% (erosions ≥2 or FL ≥2) of the possible axSpA pts could be classified as axSpA (table). Combining the various definitions of MRI-SI-s+ results in 14 additional pts (12.1%) classified as axSpA (5 pts with probability ≥80%); 5 pts fulfilled 4 of the proposed MRI-SI-s+ definitions. In pts with a high number of SpA-features, using MRI-SI-s+ to calculate the LR product results in a probability ≥80%, making an axSpA diagnosis very likely. However, in pts with only 1 or a few SpA-features, the probability remains <80%.

Conclusions These explorative data point out that SL on MRI might play a role in classifying possible axSpA pts. However, only few additional pts are classified as axSpA with a high probability while the same number of pts with a low probability would (falsely) be classified if SL would be added to the definition of a positive MRI. Further studies are needed to define the best type/combination and cut-off of SL.

References

  1. Rudwaleit ARD 2009;68:1520-7

  2. Rudwaleit ARD 2009;68:777-83

  3. Weber A&R 2010;62:3048-58

  4. Rudwaleit ARD 2004;63:535-43

Disclosure of Interest None Declared

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