EULAR/ACR classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups: A methodology report


Matteo Bottai, Karolinska Institutet
Anna Tjärnlund, Karolinska University Hospital
Giola Santoni, Stockholms universitet
Victoria P. Werth, Hospital of the University of Pennsylvania
Clarissa Pilkington, Great Ormond Street Hospital for Children NHS Foundation Trust
Marianne De Visser, Amsterdam UMC - University of Amsterdam
Lars Alfredsson, Karolinska Institutet
Anthony A. Amato, Massachusetts General Hospital
Richard J. Barohn, University of Kansas Medical Center
Matthew H. Liang, Brigham and Women's Hospital
Jasvinder A. Singh, The University of Alabama at Birmingham
Rohit Aggarwal, University of Pittsburgh
Snjolaug Arnardottir, Karolinska Institutet
Hector Chinoy, National Institute for Health Research
Robert G. Cooper, University of Liverpool
Katalin Danko, Debreceni Egyetem Általános Orvostudományi Kar
Mazen M. Dimachkie, University of Kansas Medical Center
Brian M. Feldman, Hospital for Sick Children University of Toronto
Ignacio García-De La Torre, Universidad de Guadalajara
Patrick Gordon, King's College Hospital NHS Foundation Trust
Taichi Hayashi, University of Tsukuba
James D. Katz, National Institutes of Health (NIH)
Hitoshi Kohsaka, Tokyo Medical and Dental University
Peter A. Lachenbruch, Oregon State University
Bianca A. Lang, Dalhousie University, Faculty of Medicine
Yuhui Li, Peking University People's Hospital
Chester V. Oddis, University of Pittsburgh
Marzena Olesinka, National Institute of Geriatrics, Rheumatology and Rehabilitation
Ann M. Reed, Duke University
Lidia Rutkowska-Sak, Instytut Reumatologii Warsaw
Helga Sanner, Rikshospitalet-Radiumhospitalet HF
Albert Selva-O'Callaghan, Hospital Universitari Vall d'Hebron

Document Type

Journal Article

Publication Date



RMD Open








© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted. Objective T o describe the methodology used to develop new classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIMs) and their major subgroups. Methods A n international, multidisciplinary group of myositis experts produced a set of 93 potentially relevant variables to be tested for inclusion in the criteria. Rheumatology, dermatology, neurology and paediatric clinics worldwide collected data on 976 IIM cases (74% adults, 26% children) and 624 non-IIM comparator cases with mimicking conditions (82% adults, 18% children). The participating clinicians classified each case as IIM or non-IIM. Generally, the classification of any given patient was based on few variables, leaving remaining variables unmeasured. We investigated the strength of the association between all variables and between these and the disease status as determined by the physician. We considered three approaches: (1) a probability-score approach, (2) a sum-ofitems approach criteria and (3) a classification-tree approach. Results T he approaches yielded several candidate models that were scrutinised with respect to statistical performance and clinical relevance. The probabilityscore approach showed superior statistical performance and clinical practicability and was therefore preferred over the others. We developed a classification tree for subclassification of patients with IIM. A calculator for electronic devices, such as computers and smartphones, facilitates the use of the European League Against Rheumatism/American College of Rheumatology (EULAR/ ACR) classification criteria. Conclusions The new EULAR/ACR classification criteria provide a patient's probability of having IIM for use in clinical and research settings. The probability is based on a score obtained by summing the weights associated with a set of criteria items.