Background SI-MRI is essential for diagnosing and monitoring ax-SpA. How the imaging findings relate to clinical characteristics is still poorly understood.
Objectives To clarify the relationships between the findings observed on SI-MRI and the clinical characteristics in ax-SpA.
Methods 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 SPARCC1,2 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.
Results 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, p=0.03; for ESR: R=0.84, p=0.003). 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).
Conclusions 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.
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Disclosure of Interest None declared
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