Objectives: To characterize and quantify short term changes in local inflammation using magnetic resonance imaging (MRI), and to correlate the findings with clinical disease activity in response to infliximab in patients with spondyloarthritis (SPA).
Methods: 28 consecutive patients with established SPA under successful long-term treatment with infliximab underwent MRI immediately before and one week after re-administration of the TNF blocker. CRP and BASDAI were assessed at both time points. The MRI protocol included coronal and sagittal turbo-STIR images as well as contrast-enhanced sagittal T1 weighted, fat suppressed images. Images were assessed in independent sessions using the ASspiMRI-a score, the signal-difference-to-noise ratios (SDNRs) and volumetry to assess oedematous and inflamed tissues.
Results: BASDAI values were expectedly low at study entry (3.3±2.3). One week after administration of infliximab, 46% of the patients reached a BASDAI 20, 39% a BASDAI 50. Kappa values for qualitative assessments and all measurements were excellent (range between 0.83 and 1.0) The ASspiMRI-a dropped most in the thoracic (3.3 points), less in the lumbar (1.21 points) and least in the cervical spine (0.38 points). The decrease of the ASspiMRIa, the SDNRs and the inflamed volumes in response to infliximab re-treatment was significant (p<0.01). BASDAI showed a weak correlation with the ASspiMRIa (r=0.41).
Conclusions: MRI proves to be a valid method to assess and quantify short term effects of therapy in SPA. Comparison between MRI and BASDAI changes show that the BASDAI may underestimate local inflammation. It suggests an explanation for the structural disease progression despite clinical remission.