Combined prick and patch tests for diagnosis of food hypersensitivity in dogs with chronic pruritus.

Abstract

Previous studies have shown that patch testing with food extracts can assist formulation of elimination diets (ED) in human patients with suspected adverse food reactions (AFR). Little is known about the use of these tests in dogs. To evaluate the effectiveness of a combination of prick and patch testing in current protocols, and food challenge (FC) tests in dogs with AFR. Prick and patch tests were performed on 21 dogs with chronic, nonseasonal pruritus. Dogs then were fed an ED formulated on the basis of the results. All dogs with improved clinical signs then were challenged with a food to which there had been a positive reaction in the tests. Six dogs subsequently were challenged with a food to which they had been negative on testing. Pruritus Visual Analog Scale (pVAS) and Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI-04) were evaluated on Day (D)0, D30 and D60 of the ED. Sensitivity (SE), specificity (SP), positive (PPV) and negative (NPV) predictive values, and the Kappa (κ)value were calculated. Of the 21 dogs, there was a significant mean improvement in pVAS and CADESI-04 scores in 16 (76%) dogs after D30 (P < 0.01) and D60 (P < 0.01) of the ED. There were no statistical differences between D30 and D60. The combination of tests had SE, SP, PPV, NPV and κ values of 80%, 66.7%, 66.7%, 80% and -0.17, respectively. The combination of prick and patch testing reached high values of SE and NPV. A diagnosis of AFR was made in 76% of the dogs, and test results were useful for the selection of an ED.