Validation of simplified scoring systems for assessing cutaneous disease activity in dermatomyositis

The Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) is a standard clinician-scored outcome measure for dermatomyositis (DM), but requires expertise and training. We aimed to validate simplified versions of the CDASI activity score.

Adult DM patients were prospectively enrolled with two clinic visits ≥2 months apart. Two rheumatologists independently assessed patients using the CDASI activity score (range 0-100) and the cutaneous visual analogue scale of the Myositis Disease Activity Assessment Tool (MDAAT cutaneous VAS). Additionally, patients completed the Skindex questionnaire. Four simplifications (sCDASI) were derived: (1) sCDASI-1 (range 0-66), simplified erythema to absent/present (0-1); (2) sCDASI-2 (range 0-36), simplified erythema and exclusion of scale scoring; (3) sCDASI-3 (range 0-20), simplified erythema, exclusion of scale and ulcer scoring; (4) sCDASI-4, (range 0-50), simplification of all parameters to absent/present.

Twenty-seven DM patients (81.5% female, 96.3% White, median age 50.0) were included. Median CDASI activity was 4.5 (IQR 1.0-12.0). All sCDASI scores correlated strongly with the full CDASI (Spearman ρ=0.97-0.98), MDAAT cutaneous VAS (Spearman ρ=0.94), and Skindex (Spearman ρ=0.82-0.83), indicating good convergent validity. Inter-rater reliability for all simplifications was high, as indicated by strong correlations between assessors. The changes from baseline in simplified CDASI scores correlated strongly with the changes in full CDASI scores and MDAAT cutaneous VAS, demonstrating good responsiveness.

Simplified CDASI scorings demonstrated preliminary evidence of favourable validity, reliability, and responsiveness in the longitudinal evaluation of rashes in DM patients.