0298: Accuracy of the 2017 European Alliance of Associations for Rheumatology (EULAR)/American College of Rheumatology (ACR) Classification Criteria and Myositis-Specific Autoantibodies-Based Classification Criteria for Classifying Patients with Idiopathic Inflammatory Myopathy

Tatiana Cobo¹, Marta Domínguez², Anna Pros³, Jose Luís Tandaipán⁴, Laura Nuño⁵, JULIA MARTINEZ BARRIO⁶, Vega Jovani⁷, Fredeswinda Romero⁸, Maria Esther Ruiz Lucea⁹, Eva Tomero Muriel¹⁰, Ernesto Trallero Araguás¹¹, Javier Narvaez¹², Jordi Camins Fàbregas¹³, ALBERTO MARIANO RUIZ ROMAN¹⁴, Jesus Loarce-Martos¹⁵, Annika Nack¹⁶, Esmeralda Delgado-Frías¹⁷, Francisca Sivera¹⁸, carolina Merino¹⁹, Antonio Juan Mas²⁰, Alejandro Gómez Gómez¹, Jose-Maria Pego-Reigosa²¹, Maria Martin-Lopez²², Jesús Alejandro Valero²³, Carmen carrasco-Cubero²⁴, Mercedes Freire González²⁵, Iñigo Rúa-Figueroa²⁶, Nuria Lozano Rivas²⁷, Julio David Suarez Cuba²⁸, Ana Isabel Turrión Nieves²⁹, María Ángeles Puche Larrubia³⁰ and Patricia Alcocer Amores³¹, ¹Department of Rheumatology, Hospital Universitario Infanta Sofía, Universidad Europea, Madrid, Spain, ²Sociedad Española de Reumatología, Madrid, Spain, ³Department of Rheumatology, Hospital del Mar, Barcelona, Spain, ⁴Department of Rheumatology, Hospital Universitari de la Santa Creu i Sant Pau, Barcelona, Spain, ⁵Hospital Universitario La Paz - IdiPAZ, Madrid, Spain, ⁶Rheumatology, Gregorio Marañon University Hospital, Madrid, Spain, ⁷Department of Rheumatology, Hospital General Universitario Dr. Balmis, Alicante, Spain, ⁸IIS-HU Fundación Jiménez Díaz, Madrid, Spain, ⁹Basurto University Hospital, Bilbao, Spain, ¹⁰Rheumatology, Hospital La Princesa, Madrid, Spain, ¹¹Department of Rheumatology, Hospital Universitario Vall d'Hebron, Barcelona, Spain, ¹²Hospital Universitario de Bellvitge, Barcelona, Spain, ¹³Department of Rheumatology, Hospital General de Granollers, Barcelona, Spain, ¹⁴Department of Rheumatology, Hospital Universitario Virgen del Rocío, Sevilla, Spain, ¹⁵Ramón y Cajal University Hospital, Madrid, Spain, ¹⁶Department of Rheumatology, Hospital Universitari Germans Trias i Pujol, Barcelona, Spain, ¹⁷Department of Rheumatology, Hospital Universitario de Canarias, Tenerife, Spain, ¹⁸Department of Rheumatology, Hospital General Universitario de Elda, Alicante, Spain, ¹⁹Rheumatology Department Hospital Universitario Puerta de Hierro, Majadahonda (Madrid), Spain, ²⁰Hospital Universitario Son Llàtzer, Mallorca, Spain, ²¹Rheumatology, Hospital do Meixoeiro, Vigo, Spain, ²²Hospital 12 de Octubre, Madrid, Spain, ²³Department of Rheumatology, Hospital Universitario Donostia, San Sebastián, Spain, ²⁴Department of Rheumatology, Hospital Universitario de Badajoz, Badajoz, Spain, ²⁵Rheumatology department, Complexo Hospitalario Universitario A Coruña (CHUAC). Instituto de Investigación Biomédica A Coruña (INIBIC), A Coruña, Spain, ²⁶Rheumatology, Hospital de Gran Canaria Doctor Negrin, Las Palmas de Gran Canaria, Spain, ²⁷Department of Rheumatology, Hospital Clínico Universitario Virgen de la Arrixaca, Murcia, Spain, ²⁸Department of Rheumatology, Hospital Universitario Príncipe de Asturias, Madrid, Spain, ²⁹Department of Rheumatology, Hospital Complejo Asistencial Universitario de Salamanca, Salamanca, Spain, ³⁰Department of Rheumatology, Reina Sofia University Hospital, Cordoba, Spain, ³¹Department of Rheumatology, Hospital Universitario HM Sanchinarro, Madrid, Spain

Background/Purpose: Limitations of the 2017 EULAR/ACR classification criteria have been suggested for classifying patients with idiopathic inflammatory myopathies (IIMs) and myositis-specific antibodies (MSAs). On this point, Casal-Dominguez et al recently developed a set of MSAs-based classification criteria that demonstrated perfect sensitivity and specificity (1).

The objective of this study was to determine whether the EULAR/ACR classification criteria and the MSAs-based classification criteria appropriately classify patients with IIMs, differentiating between incident and prevalent cases

Methods: Multicenter cross-sectional study of a cohort of patients included in the Spanish Registry of patients with IIM (Myo-Spain) (2). Patients were classified as incident group (time between diagnosis and study initiation ≤12 months) or prevalent group ( >12 months). The accuracy of the classification criteria according of the presence of different MSAs was described. Differences between both groups were tested by Chi-square test. The sensitivity and specificity of the MSAs-based classification criteria was determined. The percent of agreement and the Cohen's Kappa coefficient was used to measured correlations between the EULAR/ACR criteria and the MSAs-based criteria

Results: We included 542 patients with IIM diagnosis, 132 (24.4%) and 410 (75.6%) patients in the incident and prevalent group, respectively. In the overall sample, the diagnosis could be classified with the EULAR/ACR criteria in 284 patients (52.4%) and with the MSAs-based criteria in 344 patients (99.4%). Differentiating by MSAs type, patients were successfully classified by EULAR/ACR criteria as follows: 57.6 % of anti-Jo1-positive patients; 49.3% of MSAs-positive myositis patients (except anti-Jo1 antibody); 52.3% of MSAs-positive myositis patients; 52.5% of patients without MSAs antibodies (table 1). No significant differences were found between the two groups (p >0,05). Regarding MSAs-based classification criteria, patients were successfully classified as follows: 92.1% of anti-synthetase-positive patients and 100% of MSAs-positive (except anti-synthetase antibody) patients (table 2). No significant differences were found between the two groups (p >0,05).The sensitivity and specificity of the MSAs-based criteria were 100% in the incident group and 99.2% and 100%, respectively, in the prevalent group. The percentage of agreement between the EULAR/ACR criteria and the MSAs-based criteria for IIMs was 49.2% in the incident group and 50.9% in the prevalent group. This value was 48.1% and 60.2% in anti-Jo1-positive subgroup (Cohen's Kappa=0).

Conclusion: The degree of accuracy of the EULAR/ACR criteria for classifying patients with IIM diagnosis was lo, however, the MSAs-based criteria showed excellent diagnostic accuracy. No agreement was found between both classification criteria. Therefore, it seems necessary to review the classification criteria for MII, in which, in addition to including all MSAs, the difficulty in classifying patients without MSAs should be considered.

(1) Casal-Dominguez M et al. Arthritis Rheumatol 2022. (2) Cobo-Ibáñez T et al. Reumatol Clin. 2022.






T. Cobo: None; M. Domínguez: None; A. Pros: None; J. Tandaipán: None; L. Nuño: None; J. MARTINEZ BARRIO: None; V. Jovani: None; F. Romero: None; M. Ruiz Lucea: None; E. Tomero Muriel: None; E. Trallero Araguás: None; J. Narvaez: None; J. Camins Fàbregas: None; A. RUIZ ROMAN: None; J. Loarce-Martos: Boehringer-Ingelheim, 6, Bristol-Myers Squibb(BMS), 6, Galapagos, 6; A. Nack: None; E. Delgado-Frías: None; F. Sivera: AbbVie/Abbott, 1, AstraZeneca, 5, Bristol-Myers Squibb(BMS), 6, Eli Lilly, 5, 6, GlaxoSmithKlein(GSK), 6, Novartis, 5, Pfizer, 1, Roche, 5, UCB, 6; c. Merino: None; A. Mas: None; A. Gómez Gómez: Amgen, 6, Janssen, 6, Novartis, 5, Pfizer, 5, UCB, 5, 5; J. Pego-Reigosa: None; M. Martin-Lopez: None; J. Valero: None; C. carrasco-Cubero: None; M. Freire González: None; I. Rúa-Figueroa: AstraZeneca, 5, GSK, 1, 6; N. Lozano Rivas: None; J. Suarez Cuba: None; A. Turrión Nieves: None; M. Puche Larrubia: None; P. Alcocer Amores: None.