At first, I was self-diagnosed. After suffering from chronic constipation for four years, I finally realized that I was having trouble digesting white flour (wheat), so I cut it out of my diet. A few years later, I had to cut wheat out entirely in order to stay regular.
The most effective diagnostic method for me (to date) has been muscle testing. In 2006, a chiropractor who is a highly skilled kinesiologist did muscle testing on me using a test kit of 288 foods. I reacted to barley, corn, kamut, oat, rye, spelt, and wheat (but interestingly, not to millet or rice). I also reacted to shellfish, soy, yeast, chocolate (no!), cow dairy, and the artifical sweetners Equal and Sweet & Low. When I avoided all of these foods (except evidently for hidden sources), I felt much better, for a time.
In 2005, a stool test for “Gliadin AB, SIgA” was negative. In 2007, I had a blood test for gluten antibodies that was negative. More recently (2010 and 2011), two saliva tests for “Gliadin AB, SIgA” were positive.
Up until this past week when I discovered this site, I didn't know that grains other than wheat, rye, and barley contain gluten. So, I have been getting gluten exposure all along, with health issues getting worse over the past 1 1/2 years.
I am curious about the genetic testing, but I don't know if it's really necessary, given that I already know I'm gluten sensitive and must avoid gluten completely (along with my other food allergens).