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Classification Criteria

2017 European League Against Rheumatism/American College of Rheumatology Classification Criteria for Adult and Juvenile Idiopathic Inflammatory Myopathies (IIM)

The International Myositis Classification Criteria Project, a group of more than 100 myositis experts from rheumatology, dermatology, neurology and pediatric rheumatology, led by Professor Ingrid Lundberg and her research team at the Karolinska Institutet, has developed new classification criteria for myositis, which are now provisionally accepted by the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR).

The primary goals of this work have been:

  1. To develop classification criteria for use by basic and clinical researchers that distinguish the adult and juvenile idiopathic inflammatory myopathies (IIM) from other major mimicking conditions with high sensitivity and specificity; and
  2. To develop classification criteria for use by basic and clinical researchers that separate the major subgroups of the IIM from each other with high sensitivity and specificity.

The final classification criteria, which were data-driven, are based on a probability score model that provided the best sensitivity and specificity to distinguish myositis from other mimicking conditions, and include 16 variables, including age of illness onset, type and location of muscle weakness, skin manifestations, laboratory findings and muscle biopsy findings. The criteria rely on a weighted score that sums the 16 variables, and allow for flexibility in that not all variables need to be assessed to classify a patient as having myositis. The criteria encompass the major subtypes of myositis, including dermatomyositis, polymyositis, and inclusion body myositis in adults, and juvenile dermatomyositis in children. A probability score of ≥ 90% corresponds to definite IIM (corresponding to a total aggregated score of ≥ 7.5 without muscle biopsy and ≥ 8.7 with muscle biopsy) and a probability of ≥ 55% corresponds to probable IIM and is recommended as a minimum standard (corresponding to a total aggregated score of ≥ 5.5 without muscle biopsy and ≥ 6.7 with muscle biopsy) to classify a patient as having an IIM. For patients without the characteristic skin manifestations (Gottron’s papules or sign or heliotrope rash), a muscle biopsy is recommended. For patients with characteristic dermatomyositis skin findings without muscle involvement, a skin biopsy is recommended. The criteria are intended for research use and have been validated using patients who are at least 6 months from diagnosis.

Sub-classification of IIM can be made after a patient has been classified as having IIM using the 2017 EULAR/ACR classification criteria, and is based on a classification tree. Sub-classification is based on patient age at illness onset, presence of characteristic rashes of dermatomyositis, patterns of weakness, and the muscle biopsy features. It enables sub-classification of IIM into polymyositis, inclusion body myositis, dermatomyositis, amyopathic dermatomyositis, or juvenile dermatomyositis.

Publications:

  1. Lundberg IE, Tjärnlund A, Bottai M, Werth VP, Pilkington C, Visser M, Alfredsson L, Amato AA, Barohn RJ, Liang MH, Singh JA, Aggarwal R, Arnardottir S, Chinoy H, Cooper RG, Dankó K, Dimachkie MM, Feldman BM, Torre IG, Gordon P, Hayashi T, Katz JD, Kohsaka H, Lachenbruch PA, Lang BA, Li Y, Oddis CV, Olesinska M, Reed AM, Rutkowska-Sak L, Sanner H, Selva-O'Callaghan A, Song YW, Vencovsky J, Ytterberg SR, Miller FW, Rider LG; International Myositis Classification Criteria Project consortium, The Euromyositis register and The Juvenile Dermatomyositis Cohort Biomarker Study and Repository (JDRG) (UK and Ireland). 2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. Ann Rheum Dis. 2017 Dec;76(12):1955-1964. doi: 10.1136/annrheumdis-2017-211468. [Abstract]
  2. Lundberg IE, Tjärnlund A, Bottai M, Werth VP, Pilkington C, de Visser M, Alfredsson L, Amato AA, Barohn RJ, Liang MH, Singh JA, Aggarwal R, Arnardottir S, Chinoy H, Cooper RG, Dankó K, Dimachkie MM, Feldman BM, Garcia-De La Torre I, Gordon P, Hayashi T, Katz JD, Kohsaka H, Lachenbruch PA, Lang BA, Li Y, Oddis CV, Olesinska M, Reed AM, Rutkowska-Sak L, Sanner H, Selva-O'Callaghan A, Song YW, Vencovsky J, Ytterberg SR, Miller FW, Rider LG; International Myositis Classification Criteria Project Consortium, the Euromyositis Register, and the Juvenile Dermatomyositis Cohort Biomarker Study and Repository (UK and Ireland). 2017 European League Against Rheumatism/American College of Rheumatology Classification Criteria for Adult and Juvenile Idiopathic Inflammatory Myopathies and Their Major Subgroups. Arthritis Rheumatol. 2017 Dec;69(12):2271-2282. doi: 10.1002/art.40320. [Abstract]
  3. Bottai M, Tjärnlund A, Santoni G, Werth VP, Pilkington C, de Visser M, Alfredsson L, Amato AA, Barohn RJ, Liang MH, Singh JA, Aggarwal R, Arnardottir S, Chinoy H, Cooper RG, Danko K, Dimachkie MM, Feldman BM, García-De La Torre I, Gordon P, Hayashi T, Katz JD, Kohsaka H, Lachenbruch PA, Lang BA, Li Y, Oddis CV, Olesinka M, Reed AM, Rutkowska-Sak L, Sanner H, Selva-O'Callaghan A, Wook Song Y, Vencovsky J, Ytterberg SR, Miller FW, Rider LG, Lundberg IE; International Myositis Classification Criteria Project consortium, the Euromyositis register and the Juvenile Dermatomyositis Cohort Biomarker Study and Repository (JDRG) (UK and Ireland). EULAR/ACR classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups: a methodology report. RMD Open. 2017 Nov 14;3(2):e000507. doi: 10.1136/rmdopen-2017-000507. eCollection 2017. [Abstract]

Contact Information of Lead Investigator:

Not Pictured
Ingrid Lundberg, M.D., Ph.D.
Rheumatology Unit
Department of Medicine
Karolinska University Hospital
Solna, Karolinska Institutet
SE- 171 76 Stockholm, Sweden
Tel 011-46-8-5177-3080
Ingrid.Lundberg@ki.se
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