Repeatability and reproducibility of the interpretation of intradermal test results in dogs with atopic dermatitis.

Background - There is lack of studies evaluating the repeatability and reproducibility of the interpretation of intradermal testing in dogs with atopic dermatitis (AD). Objectives - To evaluate the repeatability and reproducibility of the interpretation of intradermal test results in dogs with AD. For comparison, the repeatability of allergen-specific immunoglobulin (Ig)E serology also was examined. Materials and methods - Twenty dogs with AD were used. Intradermal test included injections of known negative and positive controls, and of 25 masked injections of 10 allergens/controls, that were selected randomly and injected at random positions. Reactions to the 25 masked allergens/controls were scored (positive/negative) subjectively by three independent examiners followed by an objective assessment. Allergen-specific IgE serology was performed in blinded duplicate samples collected from all dogs for nine of 10 of the same allergens. Results - Kappa values of intraobserver repeatability (≥2 injections of the same allergen to different positions of the same dog) varied between -0.53 and 0.8 (subjective evaluations), and between 0.03 and 1 (objective evaluation). When the repeatability of the serological test was examined k = 0.91. Kappa values for the interobserver reproducibility (objective and three subjective evaluations of the same allergen injected at the same position of the same dog) varied between 0.6 and 0.74 (overall 0.67). Conclusions and clinical relevance - Intraobserver repeatability of the subjective and objective evaluation of IDT results varied from good to poor and depended on the number of times the same allergen was injected, whereas interobserver reproducibility varied from substantial to moderate. Further studies are needed to optimise the repeatability and reproducibility of IDT in dogs.