Coeliac Disease (CD) can be screened with different antibody tests in the blood (gliadin-, reticulin-, transglutaminase- and endomysium antibody tests). For a final diagnosis a small bowel biopsy must be performed to find the villous atrophy typical for CD. Especially the gliadin antibodies are quite unspecific, which means that even a high antibody concentration does not always guarantee CD to exist. Gliadin antibodies may be present also in other diseases.
One should not start a gluten-free diet before the small bowel biopsy investigation has been done. This is because the diet, kept long enough, will spoil the opportunity to perform a correct diagnosis - the villi may have recovered and the typical CD findings can no longer be seen.