Some patients with symptoms of irritable bowel syndrome may respond to a gluten-free diet. It may therefore be appropriate to consider a trial of a gluten-free diet after excluding coeliac disease and wheat allergies in order to diagnose non-coeliac gluten sensitivity (NCGS).
The relationship between irritable bowel syndrome (IBS) and coeliac disease has been the subject of considerable research interest for some time. The prevalence of undiagnosed coeliac disease amongst patients with IBS symptoms is 4%, whilst 40% of patients with newly diagnosed coeliac disease fulfil the diagnostic criteria for IBS [1,2]. In some IBS patients, particularly those with diarrhoea-predominant IBS, a gluten-free diet can bring about an improvement in symptoms even if neither coeliac 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 coeliac 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 coeliac disease [3]. Further research is required to identify whether HLA typing plays a role in identifying patients with NCGS.
References
- Sainsbury A, Sanders DS, Ford AC. Prevalence of irritable bowel syndrome-type symptoms in patients with celiac disease: a meta-analysis. Clin Gastroenterol Hepatol. 2013 Apr;11(4):359-65
- Ford AC, Chey WD, Talley NJ, et al Yield of diagnostic tests for celiac disease in individuals with symptoms suggestive of irritable bowel syndrome: systematic review and meta-analysis. Arch Intern Med. 2009 Apr 13;169(7):651-8
- Carroccio, A. et al. Non-celiac wheat sensitivity diagnosed by double-blind placebo-controlled challenge: exploring a new clinical entity. Am. J. Gastroenterol. 107, 1898–1906 (2012).
- Biesiekierski, J. R. et al. Gluten causes gastrointestinal symptoms in subjects without celiac disease: a double-blind randomized placebo-controlled trial. Am. J. Gastroenterol. 106, 508–514 (2011).
- Barmeyer C, Schumann M, Meyer T, et al. Long-term response to gluten-free diet as evidence for non-celiac wheat sensitivity in one third of patients with diarrhea-dominant and mixed-type irritable bowel syndrome. Int. J. Colorectal Dis. 2017, 32, 29–39
- Sanders DS et al. (2001) Association of adult coeliac disease with irritable bowel syndrome: a case-control study in patients fulfilling ROME II criteria referred to secondary care. Lancet; 3; 358(9292): 1504-8
- Sanders DS et al. (2003) A primary care cross-sectional study of undiagnosed adult coeliac disease. Eur J Gastroenterology & Hepatology; 15(4): 407-13
- Caio, G., Volta, U., Tovoli, F. & De Giorgio, R. Effect of gluten free diet on immune response to gliadin in patients with non-celiac gluten sensitivity. BMC Gastroenterol. 14, 26 (2014).