THU0525 DIAGNOSTIC PERFORMANCE OF MAGNETIC RESONANCE IMAGING FOR DETECTING SUBCHONDRAL BONE EROSION OF SACROILIAC JOINTS IN PATIENTS WITH SUSPECTED SPONDYLOARTHRITIS
Authors: D. Ben Nessib, H. Riahi, H. Ferjani, E. Labbene, D. Kaffel, M. Bouaziz, M. M. Kchir, F. Ladeb, W. Hamdi
Journal: Annals of the Rheumatic Diseases (2020)

Background: The utility of structural lesions of sacroiliac joints (SIJ) for the early diagnosis of spondyloarthritis (SpA) has been well established by previous reports [1]. Computed tomography (CT) is usually the preferred modality to assess structural changes. Objectives: The aim of this study was to evaluate the performance of magnetic resonance imaging (MRI) for detecting subchondral bone erosions of SIJ in patients with suspected SpA. SIJ CT findings were considered as the gold standard when interpreting results. Methods: A cross-sectional prospective monocentric study included consecutive patients aged over 16 and consulting for symptoms suggestive of SpA from February 2014 to February 2017. Patients with a confirmed sacroiliitis on pelvic radiograph were not included. Eligible patients underwent CT and MRI of SIJ. Imaging findings were assessed consensually by 2 experimented musculoskeletal radiologists, blinded to the clinical and laboratory data. Erosion was defined as resorption or destruction of the subchondral bone. The sensitivity, specificity, positive and negative predictive values of MRI for detecting SIJ erosions were determined with CT results as gold standard. Results: Fifty-four patients were enrolled: 13 men and 41 women. The average age at inclusion was 39.4 ± 11 years [17-59], and the average age at onset of symptoms was 35.6 ± 10.6 years [16-55]. Cervical, thoracic, lumbar and buttock pain were noted respectively in 46.3%,37%, 92.6%, and 57.4% of the studied patients. Sacroiliac compression test, distraction provocative test, sacral thrust test, Gaenslen’s test, Faber’s test (Patrick) and Mennel’s test were respectively positive in 23, 18, 24, 12, 28, and 17 patients. HLA B27 typing was positive in 23.4% of patients. Erosions were detected by CT scan in 30 patients. MRI showed erosions in 18 of them. A significant association was found between CT and MRI results (p=0.000), and between the presence of erosions and the diagnosis of SpA (p= 0.05 for CT and p= 0.012 for MRI). Sensitivity, specificity, positive and negative predictive values of MRI for detecting subchondral erosions were respectively estimated at 60%, 100%, 100% and 66.7%. Conclusion: Erosions of SIJ appear in early stages of SpA and have been reported in 60-90% of patients with axial SpA after mean symptom duration of 2.5 years[2, 3], hence the importance of the detection of these structural lesions. In our study, despite its moderate sensitivity, MRI showed an excellent specificity for detecting subchondral bone erosions. References: [1]Weber U, Lambert RGW, Pedersen SJ, et al (2010) Assessment of structural lesions in sacroiliac joints enhances diagnostic utility of magnetic resonance imaging in early spondylarthritis. Arthritis Care Res 62:1763–1771. https://doi.org/10.1002/acr.20312 [2]Althoff CE, Sieper J, Song I-H, et al (2013) Active inflammation and structural change in early active axial spondyloarthritis as detected by whole-body MRI. Ann Rheum Dis 72:967–973. https://doi.org/10.1136/annrheumdis-2012-201545 [3]Weber U, Lambert RGW, Østergaard M, et al (2010) The diagnostic utility of magnetic resonance imaging in spondylarthritis: an international multicenter evaluation of one hundred eighty-seven subjects. ArthritisRheum 62:3048–3058. https://doi.org/10.1002/art.27571 Disclosure of Interests: None declared