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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Rheumatology Unit, UCL Institute of Child Health, London, UK.
Hemlata
H
Varsani
Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, UK.
Susan C
SC
Charman
Rheumatology Unit, UCL Institute of Child Health, London, UK.
Charles K
CK
Li
Department of Neurology, School of Medicine, University of São Paulo, São Paulo, Brasil.
Suely K N
SK
Marie
Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Anthony A
AA
Amato
Department of Neurology, Children's Hospital of Philadelphia University of Pennsylvania, Philadelphia, Philadelphia, USA.
Brenda
B
Banwell
Department of Pathology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.
Kevin E
KE
Bove
Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Andrea M
AM
Corse
Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
Alison M
AM
Emslie-Smith
Neural Development Unit, Institute of Child Health UCL, London, UK.
Thomas S
TS
Jacques
Rheumatology Unit, Department of Medicine, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden.
Ingrid E
IE
Lundberg
Neuromuscular Disease Unit, Gaslini Institute, Genoa, Italy.
Carlo
C
Minetti
Department of Pathology, Karolinska University Hospital, Stockholm, Sweden.
Inger
I
Nennesmo
Institute for Neuropathology, University of Zurich, Zurich, Switzerland.
Elisabeth J
EJ
Rushing
Pediatric Rheumatology Unit, Department of Pediatrics, School of Medicine, University of São Paulo, São Paulo, Brasil.
Adriana M E
AM
Sallum
Dubowitz Neuromuscular Centre, Institute of Child Health UCL, London, UK.
Caroline
C
Sewry
Rheumatology Unit, Great Ormond Street Hospital NHS Foundation Trust, London, UK.
Clarissa A
CA
Pilkington
Department of Molecular Neuroscience, MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, UCL, London, UK.
Janice L
JL
Holton
Rheumatology Unit, UCL Institute of Child Health, London, UK.
Lucy R
LR
Wedderburn
D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D001706:Biopsy; D017252:CD3 Complex / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003882:Dermatomyositis / Q000378:metabolism / Q000473:pathology*; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009218:Myosins / Q000378:metabolism; D052097:Quadriceps Muscle / Q000378:metabolism / Q000473:pathology*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D000097382:CD68 Molecule
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D017252:CD3 Complex; D015395:Histocompatibility Antigens Class I; D009218:Myosins; C067980:CD68 antigen, human; D000097382:CD68 Molecule
Dermatomyositis; Disease Activity; Inflammation