Preliminary validation and clinical meaning of the cutaneous assessment tool in juvenile dermatomyositis

Objective. To provide preliminary validation of the Cutaneous Assessment Tool (CAT), a new tool to assess cutaneous manifestations of juvenile dermatomyositis (DM), and to explore the clinical meaning of CAT scores. Methods. Children with juvenile DM (n = 113) were assessed at baseline and 7-9 months later (n = 94). Internal consistency, redundancy, construct validity, and responsiveness of the CAT were examined. CAT scores corresponding to ordinal global assessments were determined. Results. Item-total correlations ranged from 0.27-0.67 for activity lesions present in ≥10% of patients; item-domain and domain-total correlations ranged from 0.25-0.99. Cronbach's alpha was 0.79 for the CAT activity score and 0.74 for the CAT damage score. As predicted, the CAT activity score correlated strongly with both global disease activity and skin disease activity and moderately with the Childhood Myositis Assessment Scale, whereas the CAT damage score correlated moderately with the physician global disease and skin disease damage scores. Median CAT activity scores of 1, 7, 13, 18, and 31 corresponded to absent, mild, moderate, severe, and extremely severe skin disease activity, respectively, Median CAT damage scores of 0, 1, 2, and 5 correlated with the same descriptions of damage (severe and extremely severe combined). Conclusion. Preliminary validation of the CAT demonstrated good internal consistency, nonredundancy, good construct validity, and appropriate responsiveness. The CAT is a comprehensive, semiquantitative assessment tool for skin disease in juvenile DM.