Mucosal challenge followed by confocal endomicroscopy is a complementary diagnostic technique, but this technology is not yet generally available and remains experimental. Other tests
Evaluating the presence of antigliadin antibodies (AGA) can be a useful complementary diagnostic test. Up to 50% NCGS patients may have elevated AGA IgG antibodies, but rarely AGA IgA antibodies (only 7% of the cases). In these patients, unlike in those with celiac disease, the IgG AGA became undetectable within six months of following a gluten-free diet. People already on a gluten-free diet
Many people remove gluten from their diet after a long history of health complaints and unsuccessful consultations with numerous physicians, who simply consider them to be suffering from irritable bowel syndrome, and some may eliminate gluten before seeking medical attention. This fact can diminish the CD serological markers titers and may attenuate the inflammatory changes found in the duodenal biopsies. In these cases, patients should be tested for the presence of HLA-DQ2/DQ8 genetic markers because a negative HLA-DQ2 and HLA-DQ8 result has a high negative predictive value for celiac disease. If these markers are positive, it is advisable to undertake a gluten challenge under medical supervision, followed by serology and duodenal biopsies. However, gluten challenge protocols have significant limitations, because a symptomatic relapse generally precedes the onset of a serological and histological relapse, and therefore becomes unacceptable for many patients. Gluten challenge is also discouraged before the age of five and during pubertal growth.It remains unclear what daily intake of gluten is adequate and how long the gluten challenge should last.
in a few people with IBS, the authors found no difference between gluten or placebo groups and the concept of NCGS as a syndrome was questioned. Nevertheless, this study had design errors and an incorrect selection of participants, and probably the reintroduction of both gluten and whey protein had a nocebo effect similar in all people, and this could have masked the true effect of gluten/wheat reintroduction. In a 2015 double-blind placebo cross-over trial, small amounts of purified wheat gluten triggered gastrointestinal symptoms (such as abdominal bloating and pain) and extra-intestinal manifestations (such as foggy mind, depression and aphthous stomatitis) in self-reported NCGS. Nevertheless, it remains elusive whether these findings specifically implicate gluten or proteins present in gluten-containing cereals. In a 2018 double-blind, crossover research study on 59 persons on a gluten-free diet with challenges of gluten, fructans or placebo, intestinal symptoms (specifically bloating) were borderline significantly higher after challenge with fructans, in comparison with gluten proteins (P = 0.049). Although the differences between the three interventions was very small, the authors concluded that fructans (the specific type of FODMAP found in wheat) are more likely to be the cause of NCGS gastrointestinal symptoms, rather than gluten. In addition, fructans used in the study were extracted from chicory root, so it remains to be seen whether the wheat fructans produce the same effect. See also
Gluten-related disorders


== References ==