FRI0238 Reliability of Sacroiliac Joint MRI Assessment in a Population-Based Cohort of Patients with Possible Inflammatory Back Pain:
Authors: U. Weber, I. Peláez-Ballestas, B. Julian, S.J. Pedersen, A. Lόpez, W.P. Maksymowych, R. Burgos-Vargas
Journal: Annals of the Rheumatic Diseases (2015)

<h3>Background</h3> A positive sacroiliac joint (SIJ) MRI based on bone marrow edema (BME) is a major criterion in the ASAS classification for axial spondyloarthritis (axSpA). Recent data suggest a comparable reliability of SIJ MRI evaluation among local and trained central readers in axSpA<sup>1</sup>. However, reproducibility of SIJ MRI assessment in a population-based cohort of patients suspected to have inflammatory back pain (IBP) is not known. <h3>Objectives</h3> To compare the reliability of SIJ MRI assessment among central readers and for central versus local readers using 2 different evaluation methods in a population-based cohort of suspected IBP patients. <h3>Methods</h3> A door-to-door survey including 4059 individuals in an urban quarter of México City identified 596 non-traumatic chronic back pain patients. 99 patients with suspected IBP at baseline (BL) and at 2-year-followup (FU) had SIJ MRI. Among patients with suspected IBP, a diagnosis of axSpA was made according to rheumatologist expert opinion (REO) after collecting all clinical, laboratory, radiographic and MRI data. SIJ MRI were assessed (a) in consensus by 4 local rheumatologists according to BME (ASAS definition<sup>2</sup>), and (b) independently by 2 calibrated central rheumatologist readers blinded to demographical/clinical characteristics and time-point of SIJ MRI. Central reads were performed both according to ASAS definition<sup>2</sup> and Global assessment<sup>3</sup> of all MRI features on T1SE and STIR sequences. We determined percent agreement in SIJ MRI evaluation between 2 central readers and for central versus local readers, both for ASAS definition<sup>2</sup> and Global assessment<sup>3</sup>. <h3>Results</h3> At BL, 99 suspected IBP patients with SIJ MRI had a mean age of 41 years (range 18-76), 60 (60.6%) were male, 2 (2%) HLA B27 positive; 1 (1%) patient met the modified New York criteria (mNYc). 9 (9.1%) patients were classified as having axSpA by REO. SIJ MRI compatible with axSpA were reported by local readers (ASAS definition) in 11 (11.1%), by central readers concordantly in 6 (6.1%) patients both for ASAS definition and Global assessment (whereof 5 same patients by both methods). Among 77 suspected IBP patients with available SIJ MRI at FU, 8 retained their classification by REO as having axSpA, 1 was newly regarded as not having axSpA, and none progressed. No additional patients became mNYc positive. Percent agreement in SIJ MRI evaluation between central readers and for central versus local readers according to ASAS definition<sup>2</sup> and to Global assessment<sup>3</sup> in a population based cohort of suspected IBP patients (Baseline n=99) <h3>Conclusions</h3> Agreement in SIJ MRI evaluation is comparable across central and local readers, both for ASAS definition and Global assessment, when applied to a population based cohort of suspected IBP patients. <h3>References</h3> Van den Berg R et al. ARD online first June 24 2014. Rudwaleit M et al. ARD 2009;68:1520. Weber U et al. ARD online first June 12 2014. <h3>Disclosure of Interest</h3> None declared