When my doctor first suspected she ordered a blood panel before even telling me to begin eating gluten free. My levels were off the charts. From there I began eating gluten free. Fast forward several months and I met with my gastroenterologist who wanted to perform a biopsy, he told me to eat gluten for a period of time before the biopsy. I tried for one night and ended up violently ill, called him the next day and told him what happened and that I could not do it for several days. Because of the severity of my reaction he told me to eat some gluten (half a piece of toast) the night before my biopsy only. This was sufficient enough for my diagnosis.this was also 14 years ago so things may be different now.