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RMD Open. 2017 Nov 14;3(2):e000507. doi: 10.1136/rmdopen-2017-000507. eCollection 2017.

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

Author information

1
Unit of Biostatistics, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
2
Rheumatology Unit, Department of Medicine, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
3
Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
4
Department of Dermatology, Philadelphia VAMC and Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
5
Department of Rheumatology, Great Ormond Street Hospital for Children NHS Trust, London, UK.
6
Department of Neurology, Academic Medical Centre, Amsterdam, The Netherlands.
7
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
8
Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
9
Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, USA.
10
Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, and Section of Rheumatology, Boston VA Healthcare System, Boston, Massachusetts, USA.
11
University of Alabama at Birmingham (UAB) and Birmingham VA Medical, Birmingham, Alabama, USA.
12
Division of Rheumatology and Clinical Rheumatology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
13
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
14
National Institute of Health Research, Manchester Musculoskeletal Biomedical Research Unit, Central Manchester University Hospitals NHS Foundation Trust, University of Manchester, Manchester, UK.
15
MRC/ARUK Institute of Ageing and Chronic Disease, Faculty of Health & Life Sciences, University of Liverpool, Liverpool, UK.
16
Division of Immunology, 3rd Department of Internal Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary.
17
Department of Pediatrics, Division of Rheumatology, University of Toronto and The Hospital for Sick Children, Toronto, Canada.
18
Department of Immunology and Rheumatology, Hospital General de Occidente, Secretaría de Salud, and University of Guadalajara, Guadalajara, Mexico.
19
Department of Rheumatology, King's College Hospital NHS Foundation Trust, London, UK.
20
Clinical Immunology, Doctoral Program in Clinical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.
21
US Department of Health and Human Services, National Institutes of Health, Bethesda, Maryland, USA.
22
Department of Rheumatology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
23
Department of Public Health, Oregon State University, Corvallis, Oregon, USA.
24
Department of Pediatrics, Division of Rheumatology, IWK Health Centre and Dalhousie University, Halifax, Canada.
25
Department of Rheumatology and Immunology, People's Hospital of Beijing University, Beijing, China.
26
Connective Tissue Diseases Department, National Institute of Geriatrics, Rheumatology and Rehabilitation, Warsaw, Poland.
27
Department of Pediatrics, Duke University, Durham, North Carolina, USA.
28
Paediatric Clinic of Rheumatology, Institute of Rheumatology, Warsaw, Poland.
29
Section of Rheumatology, Oslo University Hospital-Rikshospitalet, Oslo, Norway.
30
Vall d'Hebron General Hospital, Barcelona, Spain.
31
Department of Internal Medicine, Medical Research Center, Clinical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
32
Institute of Rheumatology and Department of Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic.
33
Division of Rheumatology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
34
Environmental Autoimmunity Group, US Department of Health and Human Services, National Institute of Environmental Health Sciences, National Institutes of Health, Bethesda, Maryland, USA.

Abstract

Objective:

To describe the methodology used to develop new classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIMs) and their major subgroups.

Methods:

An 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-of-items approach criteria and (3) a classification-tree approach.

Results:

The approaches yielded several candidate models that were scrutinised with respect to statistical performance and clinical relevance. The probability-score 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.

KEYWORDS:

autoimmune diseases; dermatomyositis; polymyositis

Conflict of interest statement

Competing interests: JAS has received research grants from Takeda and Savient and consultant fees from Savient, Takeda, Regeneron, Merz, Bioiberica, Crealta and Allergan. JAS serves as the principal investigator for an investigator-initiated study funded by Horizon pharmaceuticals through a grant to DINORA, Inc., a 501 (c)(3) entity. JAS is a member of the executive of OMERACT, an organisation that develops outcome measures in rheumatology and receives arms-length funding from 36 companies; a member of the American College of Rheumatology’s (ACR) Annual Meeting Planning Committee (AMPC); Chair of the ACR Meet-the-Professor, Workshop and Study Group Subcommittee; and a member of the Veterans Affairs Rheumatology Field Advisory Committee. HC and RGC’s work in myositis is partly funded by grants from Arthritis Research UK (18474) and the Medical Research Council (MR/N003322/1). JV’s work in myositis is supported by the Project (Ministry of Health, Czech Republic) for Conceptual Development of Research Organization 00023728.

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