Exploring erythema differences across racial groups in dermatomyositis: Implications for clinical trial outcome measures

Summary: Abstract Body: Two measurement tools are currently used to assess dermatomyositis (DM) skin disease activity: the Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) and the Cutaneous Dermatomyositis Investigator Global Assessment (CDM-IGA). As DM studies become more inclusive of cutaneous disease, it is important to utilize a scoring tool that accurately captures changes in skin activity. We aim to assess variability in erythema presentation across DM subtypes and among racial groups to help describe an outcome measure that accurately reflects improvement in DM skin disease. Our cross-sectional study included 464 DM patients enrolled in the Penn Dermatomyositis Database from January 2007 to May 2024. 84.5% of our cohort was female. 89% were White, 6.3% were Black and 3.2% were Asian. Classic (49.1%) and amyopathic (48.3%) subtypes were the most prevalent subtypes. Mean erythema, calculated using the CDASI-Activity total erythema score divided by number of affected areas at first visit, was categorized as “pink” (1.00–1.49) or “red” (≥1.50) as a surrogate for the CDM-IGA score. White (1.29±0.02), Black (1.11±0.05), and Asian (1.14±0.11) patients were all considered “pink” (p<0.01), but White patients had significantly increased average erythema compared to Black patients. CDASI severity differed across race: Whites [n=419: 50.4% mild], Blacks [n=29: 72.4% mild], and Asians [n=15: 33.3% mild] (p=0.026). However, this difference would not be observed using average erythema scores, as scored by the CDM-IGA, suggesting this measurement tool would not accurately record skin disease activity. With the need to standardize DM trial outcome measures for cutaneous disease, our findings support the use of the CDASI, a composite score which considers features other than erythema, as the primary scoring tool in cutaneous trial outcomes. Catherine Z. Shen^{1, 3}, Ari Zeidi^{1, 3}, Lilian Xie^{1, 3}, Lais Lopes Almeida Gomes^{1, 3}, Rui Feng², Victoria Werth^{1, 3} 1. Department of Dermatology, University of Pennsylvania, Philadelphia, PA, United States. 2. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA, United States. 3. Corporal Michael J Crescenz VA Medical Center, Philadelphia, PA, United States. Clinical Research: Epidemiology and Observational Research