Responsiveness and validity of the SCORFAD, an extent and severity scale for feline hypersensitivity dermatitis

Background Hypersensitivity (allergic) dermatitis (HD) is commonly seen in cats, causing pruritus and various patterns of skin lesions, including at least one of the following: head and neck excoriations, self-induced alopecia, eosinophilic plaques and miliary dermatitis. Few studies have evaluated the efficacy of therapeutic interventions for feline HD, and although various scales have been considered, none has been formally validated for the assessment of disease severity and its response to therapy. Objective To design and validate a novel scale (SCORing Feline Allergic Dermatitis; SCORFAD) to assess the value of different criteria used as outcome measures for the treatment of feline HD and to set minimal thresholds for defining the clinical success of tested interventions. Animals One hundred client-owned cats. Methods The SCORFAD scale was designed to include the four most frequently identified lesion types in feline HD (eosinophilic plaque, head and neck excoriations, self-induced alopecia and miliary dermatitis) across 10 body regions. The extent and severity of each lesion type were graded prior to inclusion and after 3 and 6 weeks in a clinical study to compare the efficacy of two doses of ciclosporin with placebo. Results The SCORFAD scale was found to exhibit satisfactory content, construct, criterion and sensitivity to change. The percentage reduction in SCORFAD from baseline was determined to be the most valid assessment of clinical response. Inter- and intra-observer reliability was not assessed. Conclusions and clinical importance The SCORFAD scale is proposed for use as a validated tool for the assessment of disease severity and response to therapeutic interventions in clinical trials for feline HD.