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Ann Rheum Dis. 2015 Jan;74(1):204-10. doi: 10.1136/annrheumdis-2013-203396. Epub 2013 Sep 24.

Validation of a score tool for measurement of histological severity in juvenile dermatomyositis and association with clinical severity of disease.

Author information

  • 1Rheumatology Unit, UCL Institute of Child Health, London, UK.
  • 2Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, UK.
  • 3Department of Neurology, School of Medicine, University of São Paulo, São Paulo, Brasil.
  • 4Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
  • 5Department of Neurology, Children's Hospital of Philadelphia University of Pennsylvania, Philadelphia, Philadelphia, USA.
  • 6Department of Pathology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.
  • 7Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
  • 8Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
  • 9Neural Development Unit, Institute of Child Health UCL, London, UK.
  • 10Rheumatology Unit, Department of Medicine, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden.
  • 11Neuromuscular Disease Unit, Gaslini Institute, Genoa, Italy.
  • 12Department of Pathology, Karolinska University Hospital, Stockholm, Sweden.
  • 13Institute for Neuropathology, University of Zurich, Zurich, Switzerland.
  • 14Pediatric Rheumatology Unit, Department of Pediatrics, School of Medicine, University of São Paulo, São Paulo, Brasil.
  • 15Dubowitz Neuromuscular Centre, Institute of Child Health UCL, London, UK.
  • 16Rheumatology Unit, Great Ormond Street Hospital NHS Foundation Trust, London, UK.
  • 17Department of Molecular Neuroscience, MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, UCL, London, UK.



To study muscle biopsy tissue from patients with juvenile dermatomyositis (JDM) in order to test the reliability of a score tool designed to quantify the severity of histological abnormalities when applied to biceps humeri in addition to quadriceps femoris. Additionally, to evaluate whether elements of the tool correlate with clinical measures of disease severity.


55 patients with JDM with muscle biopsy tissue and clinical data available were included. Biopsy samples (33 quadriceps, 22 biceps) were prepared and stained using standardised protocols. A Latin square design was used by the International Juvenile Dermatomyositis Biopsy Consensus Group to score cases using our previously published score tool. Reliability was assessed by intraclass correlation coefficient (ICC) and scorer agreement (α) by assessing variation in scorers' ratings. Scores from the most reliable tool items correlated with clinical measures of disease activity at the time of biopsy.


Inter- and intraobserver agreement was good or high for many tool items, including overall assessment of severity using a Visual Analogue Scale. The tool functioned equally well on biceps and quadriceps samples. A modified tool using the most reliable score items showed good correlation with measures of disease activity.


The JDM biopsy score tool has high inter- and intraobserver agreement and can be used on both biceps and quadriceps muscle tissue. Importantly, the modified tool correlates well with clinical measures of disease activity. We propose that standardised assessment of muscle biopsy tissue should be considered in diagnostic investigation and clinical trials in JDM.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to


Dermatomyositis; Disease Activity; Inflammation

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