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First external validation of sensitivity and specificity of the European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria for idiopathic inflammatory myopathies with a Japanese cohort
  1. Masatoshi Jinnin1,
  2. Akiko Ohta2,
  3. Shoichiro Ishihara3,
  4. Hirofumi Amano4,
  5. Tatsuya Atsumi5,
  6. Manabu Fujimoto6,
  7. Takashi Kanda7,
  8. Yasushi Kawaguchi8,
  9. Atsushi Kawakami9,
  10. Akio Mimori10,
  11. Tsuneyo Mimori11,
  12. Toshihide Mimura12,
  13. Yoshinao Muro13,
  14. Hajime Sano14,
  15. Jun Shimizu15,
  16. Tsutomu Takeuchi16,
  17. Yoshiya Tanaka17,
  18. Kazuhiko Yamamoto18,
  19. Takayuki Sumida19,
  20. Hitoshi Kohsaka20
  21. The Research Team for Autoimmune Diseases, The Research Program for Intractable Disease of the Ministry of Health, Labor and Welfare
  1. 1Department of Dermatology and Plastic Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
  2. 2Division of Public Health, Department of Social Medicine, Faculty of Medicine, Saitama Medical University, Saitama, Japan
  3. 3Department of Neurology and Neurological Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
  4. 4Department of Internal Medicine and Rheumatology, Juntendo University School of Medicine, Tokyo, Japan
  5. 5Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Hokkaido, Japan
  6. 6Department of Dermatology, University of Tsukuba, Ibaraki, Japan
  7. 7Department of Neurology and Clinical Neuroscience, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
  8. 8Institute of Rheumatology, Tokyo Women's Medical University, Tokyo, Japan
  9. 9Department of Immunology and Rheumatology, Unit of Advanced Preventive Medical Sciences, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
  10. 10Division of Rheumatic Diseases, National Center for Global Health and Medicine, Tokyo, Japan
  11. 11Department of Rheumatology and Clinical Immunology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
  12. 12Department of Rheumatology and Applied Immunology, Faculty of Medicine, Saitama Medical University, Saitama, Japan
  13. 13Department of Dermatology, Nagoya University Graduate School of Medicine, Aichi, Japan
  14. 14Department of Rheumatology, Hyogo College of Medicine, Hyogo, Japan
  15. 15Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
  16. 16Division of Rheumatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan
  17. 17The First Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Fukuoka, Japan
  18. 18Department of Allergy and Rheumatology, The University of Tokyo Hospital, Tokyo, Japan
  19. 19Department of Internal Medicine, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
  20. 20Department of Rheumatology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
  1. Correspondence to Dr Hitoshi Kohsaka, Tokyo, Japan; kohsaka-tmd{at}umin.ac.jp

Abstract

Objective To externally validate the performance of the new European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria set for idiopathic inflammatory myopathies (IIM) with a Japanese cohort.

Methods This study included 420 IIM and 402 non-IIM cases. Probability of having IIM in each patient was calculated using the collected data set. The cut-off probability was set at 55%, as recommended by EULAR/ACR. Patients classified as IIM by the criteria were further subclassified with classification trees.

Results When the probability cut-off was set at 55%, the sensitivity/specificity of the new criteria to diagnose IIM were 89.3%/91.0% in the total cohort, 88.1%/95.1% without muscle biopsy data and 90.4%/65.5% with biopsy data. The cohort included 12 overlap syndrome patients with biopsy data, who were included as non-IIM cases in accordance with traditional Japanese methods. When they were included in the IIM cases, the specificity in patients with biopsy increased to 74.4%. The sensitivity/specificity of the new criteria to diagnose polymyositis/dermatomyositis (PM/DM) plus juvenile and amyopathic DM in the Japanese cohort was 87.4%/92.4%, which were greater than those of the Tanimoto’s criteria revised to enable classification of amyopathic DM (ADM) (71.2%/87.8%) and were comparable with those of Bohan & Peter’s criteria to diagnose those diseases except for ADM (88.4%/88.3%).

Conclusions Our study externally validated high specificity of the new criteria for the first time, although with several limitations, including low percentage of child patients. The new criteria have higher sensitivity and/or specificity in classification of PM/DM than the previously reported criteria, demonstrating its usefulness for interethnic patients.

  • dermatomyositis
  • polymyositis
  • autoimmune diseases
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Footnotes

  • Handling editor Josef S Smolen

  • Contributors MJ, AO, SI and HK performed the research, analysed the data and wrote the paper. Other authors contributed to collect patients’ data. MJ and AO equally contributed to this work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient and public involvement statement The clinical data of patients were retrospectively collected from the medical records using questionnaires.

  • Patient consent for publication Not required.

  • Ethics approval The project was approved by research ethics committees of individual institutes (No. 1580).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.

  • Author note Authors’ affiliations listed were current at the time that the data collection was performed. The current address of Hajime Sano is: Department of Rheumatology, Kyoto Okamoto Memorial Hospital, Kyoto, Japan.

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