Background: The Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) and Cutaneous Assessment Tool–Binary Method (CAT-BM) have been shown to be reliable and valid outcome measures to assess cutaneous disease in adult dermatomyositis (DM) and juvenile DM (JDM), respectively. Objectives: This study compared the CDASI and CAT-BM for use by paediatric dermatologists, paediatric rheumatologists and paediatric neurologists in patients with JDM. Methods: Five paediatric dermatologists, five paediatric rheumatologists and five paediatric neurologists each evaluated 14 patients with JDM using the CDASI, CAT-BM, and skin Physician Global Assessment (PGA) scales. Inter-rater reliability, intra-rater reliability, construct validity and completion time were compared. Results: Inter-rater reliability for CDASI activity and damage scores was good to moderate for paediatric dermatologists and rheumatologists, but poor for paediatric neurologists. The inter-rater reliability for CAT-BM activity scores was moderate for paediatric dermatologists and rheumatologists, but poor for paediatric neurologists and poor across all specialties for damage scores. Intra-rater reliability for the CDASI and CAT-BM activity and damage scores was moderate to excellent for paediatric dermatologists, rheumatologists and neurologists. Strong associations were found between skin PGA activity and damage scores and CDASI or CAT-BM activity and damage scores, respectively (P < 0·002). The CDASI had a mean completion time of 5·4 min compared with that for the CAT-BM of 3·1 min. Conclusions: Our data confirm the reliability of the CDASI activity and damage scores and the CAT-BM activity scores when used by paediatric dermatologists and rheumatologists in assessing JDM. Significant variation existed in the paediatric neurologists’ scores.
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