Why quackery? As the page says the test itself is not enough for a diagnosis: the result will be interpreted based on whether your child had symptoms of food allergy in the first place (rash, bloating etc.), which is what, I believe, medical history / physical exam is referring to. If yes: that's the likely culprit; if not (and you just got this test randomly for no reason?), the chance of a false positive is 50%.