Tissue transglutaminase IgA antibody (anti-tTG IgA) is the recommended first-line screening test for celiac disease because it provides the best diagnostic sensitivity and specificity. Serum IgA should also be included to detect IgA deficiency. Tissue transglutaminase IgG antibody (anti-tTG IgG) or deamidated gliadin peptide antibodies (IgG or IgA) could be appropriate as reflex tests in specific situations based on initial findings although they have less specificity than the tissue transglutaminase IgA antibody. In particular, Deamidated Gliadin Peptides result in a higher false positive rate that can lead to further unnecessary testing and/or endoscopy.
