Intralaboratory Reliability and Variability for Allergen-Specific Immunoglobulin Type E Serology Testing

Atopic dermatitis is a very common condition affecting dogs and often managed with allergen-specific immunotherapy, which requires accurate identification of causative allergens. Serology testing is used commonly. Serum was collected from 35 atopic dogs and separated into three samples each (1, 2, and 3). Samples 1 and 2 were sent to IDEXX Laboratories the same day; sample 3 was stored at –808C and submitted w30 days later. Specific immunoglobulin type E reactivity to various allergens were determined using monoclonal anti-canine enzyme-linked immunosorbent assay (ELISA) and expressed as ELISA absorbance units. Percent difference ranged from 14.30 to 127.34% for samples 1 and 2. These values increased when comparing samples a month apart (21.78 to 129.65%). Between samples 1 and 2, for each allergen there were differences in interpretation 15.18% of the time; 32 of 35 dogs (91.4%) had at least one allergen with a different interpretation. Comparing sample 3 and the average of samples 1 and 2, differences in interpretation increased to 22.32%; all dogs had at least one allergen that was interpreted differently. These differences in interpretation can alter immunotherapy. Overall, results show the need for better reliability for allergen-specific immunoglobulin type E serology testing using monoclonal anti-canine ELISA.