Development and validation of a graphic 2D investigator's global assessment instrument for grading the overall severity of atopic dermatitis in dogs.

Abstract

Clinical trials enrolling dogs with atopic dermatitis (AD) use validated instruments that aggregate the extent and severity of selected skin lesions; none of these provides a global assessment of the severity of all lesions. To validate an Investigator Global Assessment (IGA) instrument to globally evaluate the severity of skin lesions in dogs with AD. Forty dogs with AD. A 2D graphic IGA (2D-IGA) instrument was created to subjectively score, with a single dot, the overall extent and severity of all canine AD lesions. This tool was tested for its validity (content, construct and criterion), reliability (inter- and intraobserver) and sensitivity to change. The content of the 2D-IGA was first validated by a supportive vote by the International Committee of Allergic Diseases of Animals (ICADA) membership. Its construct was verified by positive correlations between the 2D-IGA scores and those of the Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI-04) and the Canine Atopic Dermatitis Lesion Index (CADLI) (Spearman's rank-order correlation, P<0.0001). The positive correlation (P<0.0001) between an Owner Global Assessment of Disease Severity (OGADS) and the 2D-IGA indirectly satisfied its criterion. Scores graded by the same investigator hours apart and those between investigators were positively correlated (P<0.0001), thereby validating this scale's intra- and interobserver reliabilities. Finally, the changes in 2D-IGA values during treatment were correlated positively with scores of an Owner Global Assessment of Treatment Efficacy (OGATE; P<0.0001), thus showing its sensitivity to change. This novel 2D-IGA is a simple static graphic instrument that could be useful for clinical trials testing the efficacy of interventions for canine AD.