In my experience these tests were about as useless as the rest, maybe because they don't accurately test for all potential allergen anti-bodies. Bearing in mind I was already avoiding many things in my diet, for this reason certain anti-bodies weren't going to show up but beyond that it still told me certain things weren't reactive and when I continued eating them I would continue to get a reaction.
I always found the electro dermal testing, although by no means 100% to be the closest to accurate test, assuming the practitioner was experienced in using it.