In my case having the celiac (gluten) and lactose (dairy) tests come back negative kept me from removing them from my diet and delayed my getting better by years. Once I removed these I started to get better.
The tests are more suited to healthier people with allergies IMO. My gut is wounded and is intolerant of these foodstuffs and the tests were not designed for my condition.
You can use an "elimination diet" to determine what foods your gut doesn't like. It takes weeks and discipline but is very, very valuable information and only you can do it to help yourself.
The ALCAT test is a food sensitivity test, NOT a food allergy, or a test measuring IgE associated allergic responses. There is a difference. Yes, this test is expensive, it's unfortunate more people can't get it done, because I think it does work. I just started working for the R&D department of this company and had my blood drawn on my first day. My co-worker told me I might have to retake the test because for some reason I am reacting to A LOT of the foods. I never told them in my interview that I had Crohns! I can see why it's so expensive to get this stuff done because of what we do in the lab. We literally take apart EVERY SINGLE FOOD you can imagine, about 50 different chemicals/food additives, molds, everything you can possibly imagine we test for. We draw patients blood, and test it against ALL OF THOSE FOODS/CHEMICALS, depending on which panel you ordered (Most expensive panels test everything), and see what you are reacting too.
Here's one study supporting it's use. http://www.alcat.com/Images/Pdf/The_Short_Term_Efficacy_of_the_ALCAT_Test.pdf
Now before any of you go about admonishing me for supporting these tests, recognize that I have Crohns and the reason I got into this field was to get into this stuff. I really do think it's helpful. At the very least GIVE YOU THE INFORMATION to be aware of the foods which you should be skeptical about.