Allergen-specific immunotherapy (ASIT) is often discussed as though it represents a uniform treatment option. In fact, the process of customizing an allergen prescription for a pet is not standardized and there is a great deal of subjectivity involved, even when veterinarians are presented with identical test results. One veterinarian’s ASIT is not the same as the next’s ASIT.
A few years ago, I took a stab and finding out just how much variability could be expected. I invited veterinary dermatologists on the vetderm and dipderm list serves to participate. In this informal survey, 11 veterinary dermatologists responded. All were given the same patient history and allergy test results and asked for their immunotherapy recommendations. Among the findings:
- each dermatologist prescribed a unique allergen formulation
- only 2 allergens were prescribed by every participant
- the number of allergens included ranged from 10 to 20
- 28/50 allergens were prescribed by at least one dermatologist
- 16/50 allergens were prescribed by >50% of dermatologists
Now, this certainly is affected by the number of positive reactions on the test. Had there been fewer positive reactions in my hypothetical case, there would have been better agreement. But, I often see intradermal test results on second opinion cases for which 40 or more allergens are scored as positive.
When we consider the variability in test results as well as the variability in formulation recommendations, I suspect that if the same patient saw ten different veterinarians for allergy testing/ASIT, the client would get ten unique allergen prescriptions, some quite different from one another. Which is why I now refer to this treatment as subcutaneous immunotherapy rather than allergen-specific immunotherapy.