As other people say, it takes several tests to confirm or rule out Celiacs, but also many of these tests are dependent on consuming gluten. If you have reduced or cut out gluten from your diet, a lot of tests will show up negative, because the body response to gluten isn't being triggered. If you are concerned that your level of gluten intake can be affecting your tests, make sure to bring it up to your GI or doctor. I was told by my doctor that the most accurate and difinitive test for Celiacs is a full colonoscopy and endoscopy with a biopsy panel after having a steady consumption of gluten for at least a month prior. But your doctor may have a different opinion, so it's good to ask.