Background/Purpose: Translational research and clinical trials necessitate validated outcome measures to reliably assess disease progression and treatment efficacy. The Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI), a disease-specific and skin-based outcome measure, was developed for use in clinical trials and longitudinal patient assessment. The reliability and validity of this instrument have been established.¹ The goal of this study is to assess responsiveness of this tool and characterize severity and clinical response of cutaneous dermatomyositis (DM) using the CDASI.

Methods: In this two-center prospective database study the skin of patients with clinical or histologic evidence of DM was evaluated. Patients were evaluated using clinical instruments including the CDASI, a physician global assessment (PGA) 5-point Likert scale measuring disease severity (none, mild, moderate, severe, extremely severe), a PGA 0 – 10 cm visual analog scale (VAS) of disease severity and a PGA 3-point Likert scale that captured change in disease severity since the last visit (improved, worse, no change). The severity analysis compared CDASI scores for patients with mild disease to those with moderate and severe disease according to the PGA 5-point Likert. The PGA 3-point Likert and PGA VAS were used to evaluate responsiveness. Clinical response was defined as a rating of “improved” on the PGA 3-point Likert or a change in VAS scores of at least 2 cm. Statistical analysis included logistic regression models using generalized estimating equations to account for correlation among patients. A receiver operating characteristic curve was used with each model to determine cutoffs.

Results: A total of 199 patients from two sites completed up to 12 study visits each. Study participants were 79% female and 78% Caucasian. Disease subtype was classified as classic in 65% of patients and skin predominant in 35%. Separate site-specific analyses were performed due to interactions between study site and score in both the severity and responsiveness analyses. Baseline CDASI scores at the two sites range from 0 to 47 (median 17) and 0 to 48 (median 21). Data collected at one site resulted in a cutoff of 19 to differentiate mild from moderate and severe disease while at the second site CDASI scores of 14 or less characterized mild disease. Compared to the PGA VAS, the PGA 3-point Likert may be a less reliable measure of clinical response. Using a PGA VAS to assess responsiveness we found that improvement in CDASI scores of 4 or 5 indicates a clinically significant change.

Conclusion: Inter-rater variations in the use of the external PGA Likert and VAS gold measures may account for the differences between sites. The above results suggest that the CDASI is a valid and responsive tool for the evaluation of cutaneous dermatomyositis but randomized controlled trials are needed to confirm these results. 

Reference:

1. Goreshi R, Okawa J, Rose M et al. Evaluation of reliability, validity, and responsiveness of the CDASI and the CAT-BM. J Invest Dermatol2012; 132:1117-24.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validation-of-the-cutaneous-dermatomyositis-disease-area-and-severity-index-characterizing-severity-and-assessing-responsiveness-to-clinical-change/