AB1378 Clinical comparison of new criteria for inflammatory myopathy in a colombian cohort
Authors: R. Fuentes, D. Gil-Calderon, M. Cañola, J.C. Diaz-Coronado, A. Rojas-Villarraga, D. Hernandez-Parra, P. Perez-Estrada, J.C. Salazar-Uribe, R. Pineda-Tamayo
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Idiopathic inflammatory Myopathies are a group of diseases characterised by weakness due to muscle inflammation, with or without dermatological involvement, that classically includes pathognomonic findings like Gottron sign. There have been different criteria used to classify these diseases, being Peter and Bohan the most used in time, but recently the ARC/EULAR group proposed a new wat to approach the classification. <h3>Objectives</h3> To compare ACR/<sup>EULAR 2017</sup> versus Peter and Bohan criteria for Idiopathic Inflammatory Myopathy in a Colombian cohort <h3>Methods</h3> A cross-section retrospective research was done with data collected between 2014 and 2017 from a population diagnosed with Idiopathic Myopathy according to Peter and Bohan criteria and followed up for at least six months. The new ACR/EULAR criteria were applied to each individual using the online tool (hhtp://www.imm.ki.se/biosatistics/calculators/iim). Both sets of criteria were compared using Cohen's kappa coefficient and concordance was evaluated. <h3>Results</h3> Data of 149 patients were obtained. Anti-Jo1 results were not available for 75% of the patients. Biopsy was available in 44,3% of patients. Biopsy results were compatible with inflammatory myopathy in 66,7% and non-compatible in 33,3%. According to Peter and Bohan criteria the diagnosis of idiopathic inflammatory myopathy was definite in 63,1% of the patients, and probable in 27,5%. Using ACR/<sup>EULAR 2017</sup> criteria instead the diagnosis was definite in 63,1%, probable 10,1% and non-possible in 20,8%. According to the new criteria, 31 patients had polymyositis, 47 dematomyositis, 4 amyopathic dermatomyositis, 35 juvenile myositis and 1 inclusion body myositis. The concordance analysis between the two sets of criteria showed agreement of 54% (kappa 0,22 p&lt;0,001) in the whole group, 59% (kappa 0,21 p&lt;0,001) in adults, 32% (kappa 0,18 p=0,05) in children, 44% (kappa 0,05 p=0,3) in polymyositis and 42% (kappa 0,16 p=0,1) in dermatomyositis. <h3>Conclusions</h3> Data of 149 patients were obtained. Anti-Jo1 results were not available for 75% of the patients. Biopsy was available in 44,3% of patients. Biopsy results were compatible with inflammatory myopathy in 66,7% and non-compatible in 33,3%. According to Peter and Bohan criteria the diagnosis of idiopathic inflammatory myopathy was definite in 63,1% of the patients, and probable in 27,5%. Using ACR/<sup>EULAR 2017</sup> criteria instead the diagnosis was definite in 63,1%, probable 10,1% and non-possible in 20,8%. According to the new criteria, 31 patients had polymyositis, 47 dematomyositis, 4 amyopathic dermatomyositis, 35 juvenile myositis and 1 inclusion body myositis. The concordance analysis between the two sets of criteria showed agreement of 54% (kappa 0,22 p&lt;0,001) in the whole group, 59% (kappa 0,21 p&lt;0,001) in adults, 32% (kappa 0,18 p=0,05) in children, 44% (kappa 0,05 p=0,3) in polymyositis and 42% (kappa 0,16 p=0,1) in dermatomyositis. <h3>Reference</h3> [1] I. Lundberg, et al. 2017European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. Ann Rheum Dis2017;0:1–10. doi:10.1136/annrheumdis-2017-211468 <h3>Disclosure of Interest</h3> None declared