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→Laboratory Tests
===Laboratory Tests===
===Laboratory Tests===
Routine haematology and biochemistry rarely show any abnormalities in dogs, but eosinophilia is often seen in cats<sup>1</sup>.
Routine haematology and biochemistry rarely show any abnormalities in dogs, but eosinophilia is often seen in cats<sup>1</sup>. The measurement of total serum IgE levels is not useful in the diagnosis of atopic dermatitis as IgE levels do not significantly differ betweem atopic and normal animals<sup>beale</sup>. IgE levels are also influence by the presence of parasites, vaccinations and breed, and so this test is not reliable
Serum based allergy tests are widely used in the evaluation of canine atopic dermatitis. However, they are often used prior to ruling out other disorders with similar clinical signs (scabies, food allergy/intolerance). Measurement of total serum IgE levels is not a useful tool for diagnosing atopic dermatitis in dogs. IgE levels are not significantly different in dogs with atopic dermatitis than in normal healthy dogs. In addition, things like routine vaccinations and the presence of ecto or endoparasites may influence serum IgE levels. Finally, there may be breed variations in serum IgE levels.
Serum based allergy tests are only useful when a diagnosis of atopic dermatitis has already been reached by consideration of histoty and clinical exam, and by ruling out other causes of pruritus. are widely used in the evaluation of canine atopic dermatitis. However, they are often used prior to ruling out other disorders with similar clinical signs (scabies, food allergy/intolerance).
Allergen-specific IgE measurement may be used to identify allergens for immunotherapy once a clinical diagnosis of atopic dermatitis has been established. In these assays, the patient's serum is evaluated for IgE antibody directed against a panel of regional allergens (pollens, mold, dust, epidermals). Methodologies vary between laboratories, but in general, the principal is the same: the serum is allowed to react with an individual allergen extract . The unreacted antibodies are washed away, and then the allergen-bound antibody is detected using an IgE specific reagent (coupled to an enzyme or radioisotope). The IgE bound reagent is then quantified which should be proportional to the amount of allergen-specific IgE. Measurement depends on the assay utilized, but may use radiometric, fluorometric, or colorimetric measures.
Allergen-specific IgE measurement may be used to identify allergens for immunotherapy once a clinical diagnosis of atopic dermatitis has been established. In these assays, the patient's serum is evaluated for IgE antibody directed against a panel of regional allergens (pollens, mold, dust, epidermals). Methodologies vary between laboratories, but in general, the principal is the same: the serum is allowed to react with an individual allergen extract . The unreacted antibodies are washed away, and then the allergen-bound antibody is detected using an IgE specific reagent (coupled to an enzyme or radioisotope). The IgE bound reagent is then quantified which should be proportional to the amount of allergen-specific IgE. Measurement depends on the assay utilized, but may use radiometric, fluorometric, or colorimetric measures.