Evaluation of two enzyme-linked immunosorbent assays for the diagnosis of canine atopy

Serum samples from 10 dogs without skin disease, 10 with non-atopic pruritic skin disease, and 10 atopic dogs were tested blind by using two enzyme-linked immunosorbent assays (ELISAS) (Veterinary Allergy Test Kit; All-Vet [test A] and Elisarest; Bloxham Laboratories [test B]) designed to detect immunoglobulin E antibodies to environmental allergens. All the dogs tested had at least three positive reactions when using test A, and 28 of the dogs had at least one positive reaction when using test B. The median numbers of positive reactions observed in the three groups of dogs were not significantly different for each test. Significantly more reactions were observed with test A in each group (P < 0.001) than with test B. The sensitivity of both the tests was 100 per cent, but the specificity of test A was 0 per cent and the specificity of test B was 10 per cent. The positive predictive values of tests A and B were 33.3 per cent and 35.7 per cent, respectively, and the negative predictive values were 0 and 100 per cent. The poor specificities and low positive predictive values indicate that the positive results obtained when using these ELISAS are of no diagnostic value in canine atopy.