Gluten-sensitive irritable bowel syndrome

The relationship between irritable bowel syndrome (IBS) and celiac disease has been the subject of considerable research interest for some time. The prevalence of undiagnosed celiac disease amongst patients with IBS symptoms is 4%, and 40% of patients with newly diagnosed celiac disease fulfil the diagnostic criteria for IBS [1,2]. In some IBS patients, particularly those with diarrhea-predominant IBS, a gluten-free diet can bring about an improvement in symptoms even if neither celiac disease nor wheat allergy is present [3,4]. In these cases, a diagnosis of NCGS or gluten-sensitive irritable bowel syndrome should be considered.

IgG anti-gliadin antibody test

A positive IgG anti-gliadin antibody test may provide the first indication of the presence of NCGS. The prevalence of positive gliadin antibodies in the general population is around 12% but in IBS patients it is around 17% [5,6]. Furthermore, gliadin antibodies (particularly IgG anti-gliadin antibody) are elevated in around half of patients with symptoms typical of NCGS [7]. It is hypothesised that positive gliadin antibodies may be evidence of a limited immune reaction in susceptible individuals however gliadin antibodies are seen frequently in the general population and further research is required to delineate the role of anti-gliadin antibodies in the diagnosis of NCGS.
 

HLA-typing

Another potential biomarker for NCGS may be the genetic markers HLA DQ2 and DQ8. The HLA-DQ2/DQ8 haplotypes are seen in 99% of patients with celiac disease but are also seen in 25% of the general population. There is some evidence that HLA DQ2/DQ8 may be more common in NCGS compared to the general population but not to the same extent as celiac disease [3]. Further research is required to identify whether HLA typing plays a role in identifying patients with NCGS.