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Modification of the cutaneous dermatomyositis disease area and severity index, an outcome instrument
M Yassaee1, D Fiorentino, J Okawa
1Veterans Affairs Medical Center, University of Pennsylvania, Philadelphia, PA 19104-2676, USA.
Background:
Validated outcome measures in dermatology help standardize and improve patient care. A scoring system of skin disease severity in dermatomyositis known as the Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) has been developed.
Objectives:
To simplify and improve the tool for clinical research and care, we modified the CDASI and validated the new version, v2.
Methods:
The original CDASI has four activity and two damage measures. The modified CDASI has three activity and two damage measures. The skin disease of 20 patients with dermatomyositis was evaluated by the same dermatologist using both the original and the modified CDASI. Global validation measures were implemented to assess overall skin disease state, skin disease activity and skin damage. Spearman's rho (r(sp)), adjusted for multiple observations on subjects, was used to determine the relationship between the two versions of the CDASI and their correlation with the physician global measures (PGMs).
Results:
The total score and activity and damage subscores of the original and the modified CDASI correlated perfectly with each other (r(sp) = 0.99, 1.00, 1.00). The PGM-overall skin scale correlated with the total scores (r(sp) = 0.72, r(sp) = 0.76) and activity subscores (r(sp) = 0.68, r(sp) = 0.63) but not with the damage subscores (r(sp) = 0.14, r(sp) = 0.15) of the original and the modified CDASI, respectively. However, the PGM-activity and PGM-damage scales correlated with the activity (r(sp) = 0.76, r(sp) = 0.75) and damage subscores (r(sp) = 0.90, r(sp) = 0.90), respectively, of the original and the modified CDASI.
Conclusions:
The modified CDASI is perfectly correlated with the original CDASI. It has equally good concurrent validity with the PGM-overall skin and PGM-activity scales. The CDASI subscores have equally good concurrent validity with the PGM-activity and PGM-damage scales. We suggest that PGMs of skin disease activity and damage should be assessed separately for greater specificity. The modified CDASI is a refined and equally as useful outcome measure.