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Dr Lucy Wedderburn and Dr Clarissa Pilkington

• Writing in Newsletter 61
• Writing in Newsletter 60

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Dr Wedderburn writing in Newsletter 61, November 2006

The 2nd JDM Biopsy Consensus Meeting

The 2nd JDM Biopsy Consensus Meeting hosted by the JDM Research Centre (Institute of Child Health) in collaboration with the JDM Research Group (of the UK) and financially supported by the Myositis Support Group was held in March this year.

This meeting was attended by a group of international histopathology experts, now formally called the 'International Consensus Group on JDM Biopsy'. Their aim was to generate a scoring system developed during our first meeting to test the question: Which pathological changes on muscle biopsy correlate with disease severity or predict outcome in JDM?

"The scoring system was divided into 4 domains of change, these were; 1) inflammatory, 2) vascular, 3) fibrosis, and 4) muscle fibre. We developed the scoring system by discussion of what we should and how we should grade specific markers for the 4 domains above. These domains had been worked out at our first meeting. Data was presented by several members of the group from different centres, about work that had been carried out in the year between the first and second meetings and this enabled us to further fine tune the scoring system. At the end of the first day we had established a comprehensive grading criteria for the scoring of JDM muscle biopsies. To establish the scoring system each pathological feature under examination had to have its terminology and grading agreed upon by more than 8 off the 11 experts involved in the discussion. By the end of the day a new version of the scoring system had been designed and agreed by consensus. The second day took the form of a workshop. Each expert used the criteria to grade a selection of muscle biopsies from patients with varying degrees of JDM severity and normal controls; the experts did not know the patient history for any of the muscle biopsies. Statisticians worked late into the night analyzing the results of the experts and on the third day we discussed how robust the scoring system now was. During day three much discussion took place and we were able to establish what criteria were important to the scoring system, within a domain what were the critical markers and the suitable grading system for each feature within a domain. The statistical data revealed that as in 2005 some gradings within a specific domain had excellent reliability while others less good. We discussed this further and final definitions for the gradings of the scoring system were reached so that we were able to propose a final scoring system for JDM muscle biopsies.

The International Consensus Group on JDM Biopsy agreed that the work should be written up for publication as soon as possible and that prospective studies were vital in the future. This would need to be performed on a large cohort of new biopsies which have been collected with detailed clinical data. Such work would require a third meeting of the International Consensus Group on JDM Biopsy, to truly validate the scoring system as a tool.

Overall, this was a highly successful and valuable meeting. Our primary goals of finalizing a scoring tool and agreeing to publish this work were achieved."

"The work at the Institute of Child Health/Great Ormond Street Hospital on Juvenile Dermatomyositis, supported in part by funding from the Myositis Support Group, has been progressing well in the past year. We carried out a large amount of lab work to fine tune the methods that we use on biopsy preparation and staining from JDM patients. We have optimised new staining using reagents that were chosen based upon the first international JDM biopsy experts meeting (March 2005). We have also performed the work on control samples that we needed.

We are now in the process of preparing all the information and material for the second meeting, to be held in March 2006 at Institute of Child Health. We had an abstract accepted as an oral presentation at the International Paediatric Rheumatology European Society meeting 2005, and we plan to submit the final score work as a full manuscript within 2006."

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