International consensus on a proposed score system for muscle biopsy evaluation in patients with juvenile dermatomyositis: a tool for potential use in clinical trials.
OBJECTIVE
To devise and test a system with which to evaluate abnormalities on muscle biopsy samples obtained from children diagnosed with juvenile dermatomyositis (DM).


METHODS
We established an International Consensus Group on Juvenile DM Biopsy and carried out 2 phases of consensus process and scoring workshops. Biopsy sections (n = 33) were stained by standard methods. The scoring tool was based on 4 domains of change: inflammatory, vascular, muscle fiber, and connective tissue. Using a Latin square design, biopsy samples were scored by 11 experts for items in each domain, and for a global abnormality measure using a 10-cm visual analog score (VAS 0-10). The tool's reliability was assessed using an intraclass correlation coefficient (ICC) and scorer agreement (alpha) by determining variation in scorers' ratings.


RESULTS
There was good agreement in many items of the tool, and several items refined between the meetings improved in reliability and/or agreement. The inflammatory and muscle fiber domains had the highest reliability and agreement. The overall VAS score for abnormality had high agreement and reliability, reaching an ICC of 0.863 at the second consensus meeting.


CONCLUSIONS
We propose a provisional scoring system to measure abnormalities on muscle biopsy samples obtained from children with juvenile DM. This system needs to be validated, and then could be used in prospective studies to test which features of muscle pathology are prognostic of disease course or outcome. We suggest that the process we used could be a template for developing similar systems in other forms of myositis.
Wedderburn
Lucy R
LR
University College London, London, UK. l.wedderburn@ich.ucl.ac.uk
Varsani
Hemlata
H
Li
Charles K C
CK
Newton
Katy R
KR
Amato
Anthony A
AA
Banwell
Brenda
B
Bove
Kevin E
KE
Corse
Andrea M
AM
Emslie-Smith
Alison
A
Harding
Brian
B
Hoogendijk
Jessica
J
Lundberg
Ingrid E
IE
Marie
Suely
S
Minetti
Carlo
C
Nennesmo
Inger
I
Rushing
Elisabeth J
EJ
Sewry
Caroline
C
Charman
Susan C
SC
Pilkington
Clarissa A
CA
Holton
Janice L
JL
D000293:Adolescent; D001706:Biopsy; D002196:Capillaries; D002648:Child; D002986:Clinical Trials as Topic; D003882:Dermatomyositis / Q000145:classification* / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000473:pathology*