Evaluation of a direct lymphocyte proliferation test for the diagnosis of canine food allergies with delayed reactions after oral food challenge

Background: In humans, food allergies (FAs) are divided into those with immunoglobulin (Ig) E-mediated (immediate FA), cell-mediated (delayed FA) or both mechanisms (mixed FA). In dogs, lymphocyte stimulation tests have the highest concordance with oral food challenges (OFCs).

Objectives: To report the evaluation of a lymphocyte proliferation test (LPT) in dogs with FA and delayed reactions (≥6 h) after OFC.

Animals: Thirty-five healthy and 28 dogs with delayed FA.

Materials and methods: Peripheral blood mononuclear cells (PBMCs) were isolated and automatically counted before and after a 5-day culture with food allergens. Stimulation indices (SIs) were then calculated. Food allergen-specific IgE was quantified using the Pet Allergy Xplorer (PAX).

Results: None of the 10 healthy laboratory beagles and 25 healthy pet dogs had an SI greater than the 3.0 cut-off, indicating a specificity of 100%. All 28 dogs with delayed FA had at least one positive stimulation to a food item that induced delayed flares after OFC; the sensitivity of this LPT for the identification of delayed canine FA was 100%. The LPT correctly identified 57 of 68 food items causing delayed flares after OFC (84%). The PAX was negative for food-specific IgE in 18 of the 28 dogs (64%), as expected for delayed FA. In three dogs (11%), PAX results overlapped with those of the LPT, suggesting a mixed FA.

Conclusions and clinical relevance: Food allergies with delayed reactions after OFC-those suspected of having a cell-mediated mechanism-seemed to be the most common type of FA in the studied dogs. The LPT was helpful in identifying such cases.