Objective: The Cutaneous Assessment Tool (CAT) is a comprehensive, semiquantitative tool for the assessment of skin disease in juvenile dermatomyositis (DM). The goal of this study was to determine whether alternative scoring methods would shorten the CAT without compromising its measurement characteristics.
Methods: A total of 113 children with juvenile DM were assessed at baseline; 94 were assessed again 7-9 months later. Interrater reliability, internal consistency, construct validity, and responsiveness were obtained using the original scoring method and 2 alternative methods: the maximum and binary scoring methods.
Results: Spearman's correlations of the maximum and binary methods with the original were both 0.98 (P < 0.0001) for the CAT activity score, and 0.96 and 0.98, respectively (P < 0.0001), for the CAT damage score. Values obtained for interrater reliability, internal consistency, construct validity, and responsiveness were similar for all 3 scoring methods. Although there was a trend toward the maximum method having higher interrater reliability and the binary method having higher responsiveness, the confidence intervals were overlapping and no statistically significant differences were observed. Correlation coefficients for the 3 scoring methods with other measures of myositis disease activity and damage were very similar.
Conclusion: The maximum and binary methods of scoring the CAT have measurement characteristics similar to the original method. Adoption of one of these abbreviated scoring methods should increase its acceptability to clinicians and researchers.