ISSN 2398-2942      

Food allergy testing

icanis

Overview

  • Most common food allergies in dogs are to beef and wheat, but may be any dietary ingredient, especially proteins. Other allergens reported include pork, chicken, milk, egg, fish and soy, but any protein-containing foodstuff can be allergenic. One study has suggested that food allergy may account for up to 10% of all allergic disease (Scott, 1978) while the prevalence of food allergy in non-seasonal allergic skin disease has been estimated at 23% (Reedy & Miller, 1989).
  • The relevance of adverse reactions to food for GI conditions may be greater than that for dermatological signs, although these may or may not be allergic (immune-mediated) reactions.
  • Allergic breakthrough should also be considered - the clinical signs of an allergic response may only become apparent when some arbitrary threshold of immunological activity is exceeded (Brostoff & Hall, 1996) and a small increase in the total allergen load may therefore be tolerated or be sufficient to break through the allergic theshold and provoke an allergic response.
  • Detection of food-specific antibodies in blood samplemayindicate hypersensitivity to a specific food Skin: food hypersensitivity ; however, correlation with food trials has not been consistently good.
  • Identifying allergens responsible for allergy may aid in selecting a food which avoids these for a food elimination trial. The best method is to use a protein source not previously fed.
  • Recent research has shown that high levels of food-specific IgG may be better predictors of food allergy than IgE levels.
  • Several conditions may, in some cases be related to adverse reactions to food, eg gluten-sensitive enteropathy and inflammatory bowel diseases Inflammatory bowel disease: overview such as eosinophilic colitis Colitis: eosinophilic and lymphocytic-plasmacytic colitis Colitis: overview (Simpson, 1985).
  • The food allergy dermatological response in dogs is often delayed with up to 6-8 weeks of allergen-free diet to induce remission, and up to 2 weeks to provoke a relapse. This wide range of responses has made the direct connection between the clinical signs and diet more difficult to establish as compared to humans.

Sampling

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Tests

Methodologies

  • ELISA Enzyme linked immunosorbent assay (ELISA) test for IgE and IgG specific to a panel of foodstuffs common in the canine diet. For IgE, the tests are semi-quantitative and are presented as standardized scores. For IgG, values >95% of the normal reference range are reported as positive with a Class Score.
  • Food allergy tests available within 10 working days of receipt of sample.

Availability

  • YTVS is the only laboratory testing for both IgE and IgG in dogs.

Validity

Specificity

  • Inter- and intra-assay variability is <15%.
  • High incidence of asymptomatic sensitization so the detection of IgE or IgG to a specific allergen may not be clinically significant.

Predictive value

  • A negative IgE serum titer effectively excludes dietary hypersensitivity (immune-mediated allergy) to that allergen in test panel, but does not exclude dietary intolerance.
  • Elevated IgE with a positive provocative challenge test confirms food allergy.
  • Measurable food allergen-specific IgE is not present in non-food allergic individuals.
  • Recent research has shown that high levels of food-specific IgG are better predictors of food allergy than the level of IgE (Halliwell, 2004).

Technique (intrinsic) limitations

Results may not accurately predict the allergens causing clinical signs.

  • Significant antibody may be confined to mucosal surface and not present in serum.
  • Usefulness of assay is related to number of allergens included in panel.
  • Standard assay would include panel of 15 foodstuffs encompassing all the major protein and carbohydrate components of standard pet foods.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Foster A P, Knowles T G, Hotson-Moore A, Cousins P D G, Day M J & Hall E J (2003) Serum IgE and IgG responses to food antigens in normal and atopic dogs, and dogs with gastrointestinal disease. Vet Immunol & Immunopathol 92 (3-4), 113-124 PubMed.
  • Paterson S (1995) Food hypersensitivity in 20 dogs with skin and gastrointestinal conditions. JSAP 36, 529-534.
  • Guilford W G (1994) Adverse reactions to food: a gastrointestinal perspective. Comp Contin Educ Pract Vet 16, 957-969.
  • Hall E J (1994) Gastrointestinal aspects of food allergy; a review. JSAP 35, 145-152.
  • Simpson J W et al (1994) Use of a restricted antigen diet in the management of idiopathic canine colitits. JSAP 35, 233-238.
  • Rosser E J (1993) Diagnosis of food allergy in dogs. JAVMA 203(2), 259-262 PubMed.
  • Halliwell R E W (1993) The serological diagnosis of IgE-mediated allergic disease in domestic animals. J Clin Immunoassay 16(2), 103-108.
  • Jackson H & Hammerberg B (2002) Evaluation of a spontaneous canine model of IgE-mediated food hypersensitivity - changes in serum and faecal allergen-specific IgE values relative to dietary change. Comp Med 52 (4), 318-323.
  • Jeffers J G, Shanley K J & Meyer E K (1991) Diagnostic testing of dogs for food hypersensitivity. JAVMA 198 (2), 245-250 PubMed.

Other sources of information

  • Brostoff J & Hall A In: Immunology. 4th edn. Eds: Roit I, Brostoff J & Male D. Mosby, UK.
  • Wills J M & Halliwell R E W (1994) Dietary Sensitivity. In: Waltham Book of Clinical Nutrition. Pergamon. pp 167-188.
  • Reedy L M & Miller W H (1989) Allergic skin diseases in dogs and cats. W B Saunders, USA. pp 147-159.

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