FRI0587 Magnetic Resonance Imaging of the Sacro-Iliac Joints (SI-MRI) in Axial-Spondyloarthritis (AX-SPA): Correlations Between Imaging Findings and Clinical Characteristics
Authors: F. Faustini, M.C. Wick, N. Györi, P.T. Larsson, R.F. van Vollenhoven
Journal: Annals of the Rheumatic Diseases (2015)

<h3>Background</h3> SI-MRI is essential for diagnosing and monitoring ax-SpA. How the imaging findings relate to clinical characteristics is still poorly understood. <h3>Objectives</h3> To clarify the relationships between the findings observed on SI-MRI and the clinical characteristics in ax-SpA. <h3>Methods</h3> We selected 47 SI-MRI performed on ax-SPA patients between 1994 and 2013. An experienced radiologist reviewed and scored the images according to a modified version of the SPARCC<sup>1,2</sup> scoring system for SI-MRI. SI joints were assessed for bone marrow edema (BME), erosions, joint space irregularities subchondral cysts, and contrast enhancement after Gadolinium-DTPA administration. Demographic and clinical data at the time of imaging were collected retrospectively. MRI findings were analysed for correlation with clinical parameters. <h3>Results</h3> At the time of imaging the patients had mean ± SEM age of 37.4±1.7 and mean disease duration of 9.0±1.6 years. Fifty-three percent were male while the prevalence of HLA-B27 positivity was 52%. Mean disease activity as measured by the BASDAI was 5.4±0.6, while mean ASDAS-ESR was 3.0±0.3 and ASDAS-CRP was 3.1±0.3. The mean BASFI was 4.2±0.8. Mean CRP was 10.1±2.6 mg/L and mean ESR was 17.5±2.6 mm. Twenty-eight percent of the patients received TNF blockers and 60% NSAIDs. Imaging analysis revealed a prevalence of BME of 66% with a mean score of 2.4±0.4. Erosions were detected in 53% of the cases (mean score 1.4±0.3). Subchondral cysts were present in 30%, and joint space irregularities in 45% of the cases. Ankylosis was observed in 8 cases. Contrast enhancement had been performed in 15 scans and its mean score accounted for 1.2±0.3. Interestingly, this feature was significantly associated with systemic inflammation (for CRP: R=0.64, <i>p=0.03</i>; for ESR: R=0.84, <i>p=0.003</i>). The score for BME only showed a trend towards an association with ESR (R=0.30, p=0.09), while it did not associate with the CRP levels (R=0.08, p=0.64), nor with the BASDAI score (R=-0.4, p=0.13) or the ASDAS-ESR (R= -0.3, p=0.42) and ASDAS-CRP ASDAS-CRP (R=-0.38, p=0.25). Chronic damage, as expressed by the erosion mean score was not associated with disease duration (R=0.17, p=0.34) nor with the BASFI index (R=-0.03, p=0.94). Carrying the HLA-B27 antigen did not associate with a higher burden of MRI detectable inflammation or damage. Mean scores of BME in carriers compared to non-carriers (3.5±0.8 vs 2.8±0.7, p=0.47) and of erosions (2.0±0.6 vs 1.6±0.7, p=0.53) did not show statistically significant differences. HLA-B27 positivity was instead associated with a trend towards higher clinical activity by ASDAS-ESR and ASDAS-CRP (p=0.08). <h3>Conclusions</h3> In patients with ax-SpA SI-MRI findings show poor associations with clinical parameters. Although not routinely performed, the degree of contrast enhancement after Gadolinium-DTPA administration is strongly correlated with the degree of systemic inflammation. This association underlines the importance of its use in the clinical evaluation of ax-SpA patients. <h3>References</h3> Maksymowych WP, et al, Arthritis Rheum 2005 Oct 15;53(5):703-9. Wick MC, et al, J Rheumatol 2010;37(3):622-7. <h3>Disclosure of Interest</h3> None declared