Evaluation of reliability, validity, and responsiveness of the CDASI and the CAT-BM.

To properly evaluate therapies for cutaneous dermatomyositis (DM), it is essential to administer an outcome instrument that is reliable, valid, and responsive to clinical change, particularly when measuring disease activity. The purpose of this study was to compare two skin severity DM outcome measures, the Cutaneous Disease and Activity Severity Index (CDASI) and the Cutaneous Assessment Tool-Binary Method (CAT-BM), with the Physician Global Assessment (PGA) as the "gold standard". Ten dermatologists evaluated 14 patients with DM using the CDASI, CAT-BM, and PGA scales.