THU0422 Performance of eular/acr 2017 idiopathic inflammatory myopathies clasification criteria in a real world cohort
Authors: R.A. Gómez, A. Braillard Poccard, M. Pino, G. Medina, D. Dubisnky
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Idiopathic Inflammatory Myopathies (IIM) are an heterogeneous group of multisystemic diseases. It includes Polimyositis (PM), Dermatomyositis (DM) with its clinicaly amiopathic variant (CADM), the antisynthetase syndrome (ASS), the inclusion body myositis (IBM), Immune-mediated necrotising myopathy (IMNM), the juvenile variants of DM/PM and the connective tissue disease-myosits overlap (CTD-OM). Distintion between subtypes is made on grounds of clinical features, histologic findings at muscle biopsy and presence of certain autoantibodies. Multiple classification criteria had been proposed through time, EULAR/ACR been the most recent. However, their performance in patients from common practice in Latin America had not been widely evaluated. In our practice, access to muscle biopsy and electromyogram (EMG) is not always available <h3>Objectives</h3> To evaluate the performance of the EULAR/ACR 2017 IIM classification criteria in a real world cohort and compare it with the performance of other classification criteria <h3>Methods</h3> Retrospective study. IIM patients defined by expert opinion followed in our centre between <sup>October 2007</sup> and November 2017 were included. The patients were classified clinically in DM, CADM, PM, ASS and CTD-OM. Patients with positive antisynthetase antibodies were reclassified as ASS. Availability of EMG, muscle biopsy and anti Jo-1 antibodies was evaluated. , Bohan &amp; Peter (1975) Tanimoto (1995) y EULAR/ACR (2017) criteria were applied to the population <h3>Results</h3> 60 patients were included. DM 20 (33.3%), CADM 4 (6.66%), PM 4 (6.66%), ASS 10 (16.66%) y CTD-OM 22 (36.66%). Muscle biopsy available 14/60 (23.33%), EMG available 33/60 (55%) and anti Jo-1 determination available in 57/60 (95%). In general, 12/60 (20%) classified as defined disease by Bohan and Peter criteria, 29/60 (48.3%) by Tanimoto criteria and 34/60 (56.6%) by EULAR/<sup>ACR 2017</sup> criteria. Extending the classification to probable besides defined, 38/60 (63.3%) met Bohan and Peter criteria and 51/60 (85%) met EULAR/ACR criteria. Table 1 shows percentage of patients meeting each criteria set by clinical subtype. Patients with available muscle biopsy (n=14) were subanalyzed: 11/14 (78.6%) muscle biopsy were compatible with IIM (3 not compatible, but previously treated). DM 3/11 (28.6%), ASS 1/11 (7.14%) y CTD-OM 7/11 (50%). 7/11 (50%) met Bohan and Peter criteria, 8/11 (78.6%) met Tanimoto criteria and 8/11 met EULAR/ACR criteria. If extended to probable cases, 11/11 (100%) met Bohan and Peter criteria and 10/11 (91%) EULAR/ACR criteria. Table 1 Fullfillment of different criteria set by IIM subtype <h3>Conclusions</h3> EULAR/<sup>ACR 2017</sup> performed especially well for DM, and were the only criteria set met by CADM patients. PM patients failed to meet Bohan and Peter and EULAR/ACR criteria for definite disease, probably due to low availability of EMG and muscle biopsy. This was similar for pure PM and PM/CTD-OM. Tanimoto criteria were the most sensitive for clasification of ASS patients, which could be explained because they consider arthritis among clinical features. When considering probable and defined cases, EULAR/ACR criteria were highly sensible in this real world cohort <h3>Disclosure of Interest</h3> None declared