AB1421 DOES THE SACROILIAC JOINT MAGNETIC RESONANCE IMAGING ENHANCE THE ENTHESITIS-RELATED ARTHRITIS DIAGNOSIS?

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Background Magnetic Resonance Imaging (MRI) is the gold standard in the diagnosis of adult spondyloarthritis [1]. MRI sensitivity and specificity seem to be less studied in juvenile spondyloarthritis, especially in Enthsitis-related Arthritis (ERA). Objectives We aimed to determine the sensitivity and specificity of MRI in the diagnosis of ERA. Methods We conducted a retrospective study including 44 patients with Juvenile Idiopathic Arthritis (JIA) meeting the International League of Associations for Rheumatology (ILAR) 2001 criteria. For each patient, we collected the following data: age, age at the onset of JIA, JIA subtype, disease duration, C-reactive protein (CRP), HLA-B27 typing, and Erythrocyte sedimentation rate (ERS) levels. Each patient had a sacroiliac joint MRI. Sacroiliitis was defined using the OMERACT JAMARIS scoring system [1]. Disease activity was assessed using the JSpADA score for ERA and JADAS-CRP-10 for the rest of the JIA subtypes. We divided patients into two groups: Group 1 (G1) patients with ERA and Group 2 (G2) patients with non-ERA subtype. Statistical analysis was performed using SPSS software. Results We included 28 boys and 16 girls. The mean age was 13.65 ± 4.62 years. The mean age at the onset of the disease 9.57 was ± 3.97 years. The mean disease duration was 4.34 ± 3.09 years. There was enthesitis-related arthritis in 61% of the cases (n=27), oligoarticular JIA in 14% of the cases (n=6), polyarticular JIA in 11% of the cases (n=5), and psoriatic arthritis in 7% of the cases (n=3). JIA was undifferentiated in 7% of the cases (n=3). Sacroiliac joints were painful in 15 patients (34%). The mean CRP and ESR were 14.42 ± 19.67mg/L and 26.56 ± 20.87mm, respectively. The mean JADAS and JSpADA were 6.6 ± 4.7 and 3.09 ± 1.55, respectively. HLA-B27 was performed in 22 patients and was positive only in five patients. IRM was normal in 25 patients (57%) (G1: 11 versus G2:14) and showed bone marrow in the sacroiliac joints in 19 patients (34%) (G1=16 versus G2=3, p=0.005). The sensitivity and specificity of the sacroiliac joints MRI in the diagnosis of ERA were 61.54% and 82.35%, respectively. Positive predictive value and negative predictive value were 84.21% and 58.33%, respectively. Furthermore, sacroiliac joint pain in the clinical examination was able to predict sacroiliac bone edema in MRI with an odds ratio of 6.8 (95% confidence interval 1.68 to 28.09; p=0.006). Conclusion According to other studies, ours showed that MRI inflammatory lesions could be observed in JIA regardless of JIA sub-types [2]. Interestingly, we found that MRI abnormalities were not sensitive but had a good specificity in the diagnosis of ERA. Thus, MRI could guide the diagnosis of ERA but could not be the gold standard in this disease. References [1] Herregods N, Maksymowych WP, Jans L, et al. Atlas of MRI findings of sacroiliitis in pediatric sacroiliac joints to accompany the updated preliminary OMERACT pediatric JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system: Part II: Structural damage lesions. Semin Arthritis Rheum. 2021;51(5):1099-1107. [2] Demir S, Ergen FB, Taydaş O, et al. Spinal involvement in juvenile idiopathic arthritis: what do we miss without imaging?. Rheumatol Int. 2022;42(3):519-527. Acknowledgements: NIL. Disclosure of Interests None Declared.

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