OP0160 Classification of Axspa Based on Positive Imaging (Radiographs and/or MRI of the Sacroiliac Joints) by Local Rheumatologists or Radiologists versus Central Trained Readers in the Desir-Cohort
Authors: R. van den Berg, G. Lenczner, F. Thévenin, P. Claudepierre, A. Feydy, M. Reijnierse, A. Saraux, A. Rahmouni, M. Dougados, D. van der Heijde
Journal: Annals of the Rheumatic Diseases (2014)

<h3>Background</h3> Sacroiliitis on MRI and X-rays play an important role in the ASAS axial spondyloarthritis (axSpA) criteria<sup>1</sup>. Though, recognition of sacroiliitis on X-rays (X-SI) and MRI of the sacroiliac joints (MRI-SI) can be challenging, resulting in misinterpretations. Usually the reading in clinical trials is done by ≥1 trained readers. In cohorts it varies and in the DEvenir des Spondylarthropathies Indifferenciées Récentes (DESIR)-cohort, X-SI and MRI-SI at inclusion are read by a local radiologist/rheumatologist. The impact on classification of patients (pts) by local read (LocR) instead of centralized read (CentR) is unknown. <h3>Objectives</h3> To investigate the difference in classification of pts (ASAS axSpA) using LocR versus CentR as external standard. <h3>Methods</h3> In the DESIR-cohort, pts aged 18-50 with inflammatory back pain (IBP; ≥3 months, ≤3 years) were included (n=708). Local radiologists/rheumatologists read all baseline X-SI and MRI-SI; X-SI according to a method derived from the modified New York (mNY) criteria<sup>2</sup> (grade 2 and 3 pooled in one combined grade “DESIR-2”). Sacroiliitis was defined by at least unilateral ≥DESIR-2. Sacroiliitis on MRI was defined as definite inflammatory lesions in ≥1 SI-joint. Next, 2 well-calibrated central readers independently read all X-SI (original mNY) and MRI-SI (ASAS<sup>3</sup>). An experienced radiologist was adjudicator in case the 2 readers disagreed. An image was marked positive if 2/3 readers agreed. Subsequently, LocR was compared to CentR and to the reads by the central readers separately; pts were classified (ASAS axSpA), using both LocR and CentR (external standard). <h3>Results</h3> Pts with onset IBP &lt;45 and complete X-SI and MRI-SI (n=582) were included. LocR and CentR differed in 163/582 pts (28%; 91 X-SI; 59 MRI-SI; 13 both X-SI and MRI-SI). In 46/582 pts (7.9%), a different read resulted in a different classification; 18 no-SpA pts (3.1%) based on CentR were classified as axSpA using LocR (14 with positive X-SI); 28 axSpA pts (4.8%; 13 mNY+) based on CentR were classified as no-SpA using LocR (table). Among the patients classified as axSpA, additional discrepancies occurred if fulfilling the imaging arm was considered; 16 axSpA/582 pts (2.7%; 8 mNY+) fulfilled the imaging arm based on CentR but fulfilled the clinical arm based on LocR, and 29 axSpA pts (5.0%) fulfilled the clinical arm based on CentR but fulfilled the imaging arm based on LocR (table). Comparisons of LocR versus the separate readers show very similar results (table). <h3>Conclusions</h3> Looking at the complete ASAS axSpA criteria, the classification changed in 7.9% of the pts when using LocR instead of CentR. However, when interested in whether pts fulfil the imaging arm or not, changes are seen in an additional 8.2% of the pts resulting in 15.6% of the pts classified differently. <h3>References</h3> Rudwaleit ARD 2009;68:777-83. van der Linden A&amp;R 1984;27:361–8. Rudwaleit ARD 2009;68:1520-7. <h3>Disclosure of Interest</h3> None declared <h3>DOI</h3> 10.1136/annrheumdis-2014-eular.1617