The purpose of this study was to define the operational and performance characteristics of a commercially available monoclonal antibody based (mac) ELISA for detection of allergen-specific IgE in dogs. The average intra-assay variance over 1 year was 9.7% (range 2.5-62.7%), while the interassay variance averaged 10.8% (range 8.1-13.8%). The average positive control responses observed for grass, weed, tree and mite allergens during each month remained relatively constant; the average monthly variance was 11.6% (range 8.3-19.2%) for grass pollens, 13.3% (range 9.1-20.4%) for weed pollens, 13.3% (range 9.8-18.2%) for tree pollens and 13.6% (range 8.9-18.7%) for mite allergens. The interlaboratory concordance of results for the macELISA was approximately 91%. The interlaboratory concordance of results comparing the macELISA and a high affinity IgE receptor-based ELISA was approximately 92%. The results demonstrate that the macELISA is reproducible and the results are comparable to the high affinity IgE receptor based ELISA within and between laboratories.

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In vitro cross-reactivity among two house dust (Dermatophagoides farinae, D. pteronyssinus) and three storage (Acarus siro, Tyrophagus putrescentiae, Lepidoglyphus destructor) mites was examined in 20 mite-sensitive dogs with natural occurring atopic dermatitis (group A), 13 high-IgE beagles experimentally sensitized to D. farinae (group B), and five healthy beagles (group C). Intradermal testing (IDT) and serology for allergen-specific IgE demonstrated that co-sensitization for all possible pairs of the five mites was generally 45% or higher among group A dogs. In the same dogs, enzyme-linked immunosorbent assay cross-inhibition results indicated that each one of D. farinae, A. siro and T. putrescentiae was a strong inhibitor of all the remaining mites, whereas D. pteronyssinus was a strong inhibitor of L. destructor. A high number of positive IDT and serology test results for D. pteronyssinus, A. siro, T. putrescentiae and L. destructor were recorded among group B dogs. No conclusive evidence of exposure to these mites was found upon analysis of dust samples from their environment and their food for the presence of mites and guanine. Also, the number of positive test results was generally higher among group B than among group C dogs. Enzyme-linked immunosorbent assay cross-inhibition revealed that D. farinae was a strong inhibitor of D. pteronyssinus, A. siro and T. putrescentiae. Collectively, these results demonstrated extensive in vitro cross-reactivity among house dust and/or storage mites that can explain false-positive results upon testing of dust mite-sensitive dogs with atopic dermatitis.

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