@article{Maksymowych2019, abstract = {ObjectivesThe Assessment of SpondyloArthritis international Society (ASAS) MRI working group (WG) was convened to generate a consensus update on standardised definitions for MRI lesions in the sacroiliac joint (SIJ) of patients with spondyloarthritis (SpA), and to conduct preliminary validation.MethodsThe literature pertaining to these MRI lesion definitions was discussed at three meetings of the group. 25 investigators (20 rheumatologists, 5 radiologists) determined which definitions should be retained or required revision, and which required a new definition. Lesion definitions were assessed in a multi-reader validation exercise using 278 MRI scans from the ASAS classification cohort by global assessment (lesion present/absent) and detailed scoring (inflammation and structural). Reliability of detection of lesions was analysed using kappa statistics and the intraclass correlation coefficient (ICC).ResultsNo revisions were made to the current ASAS definition of a positive SIJ MRI or definitions for subchondral inflammation and sclerosis. The following definitions were revised: capsulitis, enthesitis, fat lesion and erosion. New definitions were developed for joint space enhancement, joint space fluid, fat metaplasia in an erosion cavity, ankylosis and bone bud. The most frequently detected structural lesion, erosion, was detected almost as reliably as subchondral inflammation (κappa/ICC:0.61/0.54 and 0.60/0.83) . Fat metaplasia in an erosion cavity and ankylosis were also reliably detected despite their low frequency (κappa/ICC:0.50/0.37 and 0.58/0.97).ConclusionThe ASAS-MRI WG concluded that several definitions required revision and some new definitions were necessary. Multi-reader validation demonstrated substantial reliability for the most frequently detected lesions and comparable reliability between active and structural lesions.}, author = {Maksymowych, Walter P. and Lambert, Robert Gw and Østergaard, Mikkel and Pedersen, Susanne Juhl and Machado, Pedro M. and Weber, Ulrich and Bennett, Alexander N. and Braun, Juergen and Burgos-Vargas, Ruben and de Hooge, Manouk and Deodhar, Atul A. and Eshed, Iris and Jurik, Anne Grethe and Hermann, Kay-Geert Armin and Landewé, Robert Bm and Marzo-Ortega, Helena and Navarro-Compán, Victoria and Poddubnyy, Denis and Reijnierse, Monique and Rudwaleit, Martin and Sieper, Joachim and Van den Bosch, Filip E. and van der Heijde, Désirée and van der Horst-Bruinsma, Irene E. and Wichuk, Stephanie and Baraliakos, Xenofon}, doi = {10.1136/annrheumdis-2019-215589}, journal = {Annals of the Rheumatic Diseases}, month = {aug}, pages = {1550-1558}, title = {MRI lesions in the sacroiliac joints of patients with spondyloarthritis: an update of definitions and validation by the ASAS MRI working group}, url = {https://oadoi.org/10.1136/annrheumdis-2019-215589}, volume = {78}, year = {2019} }