Evaluating important change in cutaneous disease activity as an efficacy measure for clinical trials in dermatomyositis.

backgroundPatients may experience improved quality of life (QoL) without complete clearance of skin disease. The Cutaneous Dermatomyositis Disease Area and Severity Index Activity (CDASI-A) score correlates with the Symptoms and Emotions subscales of Skindex-29, a measure of QoL, down to CDASI-A scores of 7 points (for Symptoms) and 10 points (for Emotions).

objectivesOur goal was to define an important change in disease activity, as measured by the CDASI-A, that results in a meaningful change in QoL in patients with dermatomyositis.

methodsIn 103 patients, we assessed the percentage change and actual change in CDASI-A scores needed to achieve a meaningful improvement in QoL, using linear regression models.

resultsWe found that meaningful improvement correlates with 7·86 points (P < 0·001) in Symptoms, and 10·29 points (P < 0·001) in Emotions, after correlating Skindex-29 to an established definition of meaningful change in the Dermatology Life Quality Index (DLQI). For patients with initial CDASI-A scores > 14 points, a 40% change in CDASI-A between the first two visits suggests a meaningful change in Skindex-29. In patients with moderate initial CDASI-A (15-26 points), the changes in CDASI-A resulting in meaningful changes in Symptoms and Emotions were 6 points (P < 0·001) and 7 points (P < 0·001), respectively. For initial CDASI-A scores in the severe range (27-35 points), an improvement in CDASI-A by 11 points (P = 0·030) and 9 points (P = 0·021) leads to a meaningful change in Symptoms and Emotions, respectively.

conclusionsIn patients with an initial CDASI-A score > 14 points, a 40% change in the CDASI-A score can be used to indicate a meaningful change in QoL in future dermatomyositis trials. What's already known about this topic? The Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) is a validated disease assessment tool used to capture the extent of cutaneous activity and damage. The Skindex-29 and Dermatology Life Quality Index are standardized and validated measures of quality of life (QoL) for clinical trials and correlate with CDASI Activity (CDASI-A) scores. What does this study add? We identified what change in Skindex-29 scores over two consecutive visits would indicate an important change (a minimal clinically important difference) in QoL. We determined which change in CDASI-A scores over two consecutive visits would lead to a meaningful change in QoL. For patients with an initial CDASI-A score > 14 points, a 40% change in the CDASI-A score over two visits is associated with a meaningful change in QoL. What are the clinical implications of this work? Clinical trials can consider using a 40% change in the CDASI-A score as an end point when assessing the clinical efficacy of drugs.