Background/Purpose: Spinal MRI lesions suggestive of axial Spondyloarthritis (axSpA) are not included in the ASAS definition of a positive MRI, but do occur in the absence of affected sacroiliac joints (SIJ). It is unknown how often this happens and if it is useful to perform a MRI of the spine in patients (pts) with negative MRI-SIJ. The objective of this study was to investigate the prevalence of a positive MRI-spine in pts with short symptom duration and a negative MRI-SIJ

Methods: Pts aged 18-50 with inflammatory back pain (IBP) (≥3 months, ≤3 years) from 25 participating centers in France were included in the DESIR-cohort (n=708). All available baseline MRIs of the spine were independently scored by 2 well-calibrated central readers who were blind to any other data. MRIs-SI were scored according to the ASAS definition¹ (lesions highly suggestive of sacroiliitis plus ≥1 lesion on ≥2 consecutive slices or >1 lesion on 1 slice). Inflammatory lesions on MRI-spine suggestive of spondylitis were scored when visible on ≥2 consecutive slices and according to the ASAS consensus definition² (≥3 lesions). In case of disagreement, an experienced radiologist served as adjudicator. MRI was considered positive if 2/3 readers agreed.

Results: All pts with MRI-spine and MRI-SIJ (n=650) were included in the analyses. There were 231 pts (35,5%) with a positive MRI-SIJ and 102 pts (15.7%) with a positive MRI-spine; 67 pts (10.3%) were positive for both MRI-SIJ and MRI-spine, 384 (59.1%) were negative for both; and 35 pts (5.4%) had a positive MRI-spine but a negative MRI-SI. Thirty of these were <45 years at symptom onset (entry criterion for ASAS axSpA criteria); 8 of these 30 pts fulfilled the modified New York criteria, 16 of these 30 pts fulfilled the clinical arm of the ASAS axSpA criteria and 6 pts did not fulfil the criteria. All these 6 pts were HLA-B27 negative. Therefore, if the MRI-spine would be considered to count for imaging for the ASAS criteria, 6 additional pts would have been classified and 16 pts would have fulfiled both the imaging and clinical arm; Two of the 5 pts with age >45 years at symptom onset fulfilled the mNY criteria.

Overall, only 25 pts (3.8%) had a pos MRI-spine without sacroiliitis on MRI or radiographs.

Conclusion: In 3.8% of IBP pts aged 18-50 ≥3 spinal inflammatory lesions suggestive of axSpA are found in absence of sacroiliitis on MRI or radiograph. Therefore the yield of including MRI-spine as additional imaging criterion in the ASAS axSpA classification criteria is considered unacceptably low.

References:¹Rudwaleit ARD 2009;68:1520-7 ²Hermann ARD 2012;71:1278-88

---

« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-it-worth-it-to-include-mri-of-the-spine-in-the-asas-classification-criteria-for-axial-spondyloarthritis/