Background According to the ASAS axial Spondyloarthritis (axSpA) classification criteria, only lesions at the sacro-iliac level (structural damage at plain XRays or inflammation at MRI) have to be considered. However, other lesions at a different location or at other imaging modalities might also be observed.
Objectives to evaluate different imaging abnormalities (e.g. inflammatory and structural changes at the sacroiliac joint (SIJ) and spine level) observed at an early stage in axial SpA
Methods Prospective, multi-centre, observational study. 708 patients with early inflammatory back pain suggestive of spondyloarthritis have been included in the DESIR cohort. Demographics, items of the ASAS axSpA criteria, disease activity, severity, quality of life were collected. Inflammatory and structural changes evaluated using either X-rays or MRI at both the SIJ and spine level. Statistical analysis: patients fulfilling the ASAS axSpA criteria were splitted in two groups (imaging vs. clinical) and within the clinical arm, with regard to the presence of CRP abnormality (>6mg/L). The other imaging abnormalities suggestive of SpA (ie. MRI structural changes of SIJ, MRI inflammatory and structural changes of the spine, and the presence of at least 1 syndesmophyte at the cervical/lumbar level) present in each of the groups were depicted.
Results Because of missing data, 682 of the 708 recruited patients could be classified according to the ASAS criteria; 476 (69.8%) fulfilled such criteria. Structural damage at X-ray(n=55, 8.1%), inflammation at MRI (99, 14.5%), or both (132, 19.4%) permitted to consider 286 (41.9%) patients as fulfilling the imaging arm of the ASAS criteria. The table summarizes the different imaging abnormalities observed in the different sub-groups of patients.
MRI chronic changes of the SIJ were, more frequently observed in the subgroup of patients with X-ray damage of the SIJ (64.17%), but more interestingly, also in 4.3% patients of the clinical arm. MRI inflammatory changes of the spine were more frequently observed in presence of other markers of inflammation (e.g. local MRI inflammatory changes of the SIJ [39.4%] or CRP abnormality [21.2%]). Furthermore in the subgroups of patients without X-ray sacroiliitis, as much as 8.1%, 9.1% and 6.5% of patients presented with definite X-ray damage of the spine (“MRI sacroiliitis and X-ray negative”, “MRI negative and X-ray negative, CRP abnormal” and “MRI negative and X-ray negative, CRP normal”, subgroups respectively).
Conclusions This study shows that different imaging abnormalities suggestive of SpA (e.g. MRI chronic changes of the SIJ) are present in early SpA. Descriptive studies of these abnormalities in healthy controls are necessary to confirm (or not) whether these findings could be considered for revisiting the definition of the imaging arm of the ASAS criteria.
Acknowledgements This study was finantially supported by a Pfizer grant.
Disclosure of Interest None Declared