i can only answer the question with respect to humans, but I imagine the principles outlined would apply to other species. Assessment of total IgE as a predictor of allergy (more accurately atopy) is statistically contingent on the sensitivity and specificity of a particular value. As you know, total IgE is a graph or curve, you can work out the statistical likelihood of atopy from a particular value of total IgE by knowing the normal range for dogs from a particular laboratory and knowing the sensitivity and sensitivity of that test from that lab.
In humans we would not, however, prescribe allergen immunotherapy unless specific sensitivity were identified by specific IgE or allergen skin tests, no matter how high the total IgE.
Furthermore, in humans there are a number of non-allergy related causes of elevated total IgE.
But clearly I am not a vet and I could stand corrected by someone in vet science!
I think I can only absolutely agree with you, as I also started my allergy studies in humans. Used the Cap System first and then the Unicap, since it was launched in 1995 at the Madrid EAACI meeting. Unfortunately, the much user friendly Unicap revealed to be a little worse for inhibition assay studies... In vet Med we are still using a few ELISA protocols for specific IgE determination and I´m sure that a proper coating with an anti-dog- IgE will be also suitable for total IgE.
As you told for humans, it happens the same regarding dogs: there is not a direct correlation between specific IgE, IDT (we uses IDT, since pricks are about to lead to more false negative results - estimated in 20% more), the number of molecular allergens identified from Western Blottings, or even the clinical pattern or severity. This is more or less similar to humans. Although, as I read from humans, if an individual presents a high cluster of those parameters, the level of total IgE, it is more about to be an atopic and that is what I wanted to verify/prove for dogs.
I add the proposed abstract of a review manuscript I’ve sent and that is under review. It talks about vet allergy diagnosis evolution during the last 25-30 years, comparing to humans. I hope we can discuss more about these issues.
I also agree with the most you answered. In fact, even talking about specific IgE, many times the presence and even the levels are not the marker for atopy. Atopy or allergy in general, I think that even in type I hypersensitivity it is a cellular issue in the presence of specific IgE. Some humans and dogs, as well, with relevant levels of specific IgE are not allergic.
Best wishes/ melhores cumprimentos - seria muito interessante e estrategicamente vantajoso o estabelecimento de uma rede de alergia veterinária nos países de expressão portuguesa - fica aqui o desafio.